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| <h1 class="post-title-main">Detecting a sensor value out of expected range</h1> |
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| |
| <p>Oftentimes, a user expects a sensor value to fall within a particular range. If a reading is outside the accepted limits, the user may want to determine what caused the anomaly and/or take action to reduce the impact. For instance, consider the following scenario.</p> |
| |
| <p>Suppose a corn grower in the Midwestern United States would like to monitor the average temperature in his corn field using a sensor to improve his crop yield. The optimal temperatures for corn growth during daylight hours range between 77°F and 91°F. When the grower is alerted of a temperature value that is not in the optimal range, he may want to assess what can be done to mitigate the effect.</p> |
| |
| <p>In this instance, we can use a filter to detect out-of-range temperature values.</p> |
| |
| <h2 id="setting-up-the-application">Setting up the application</h2> |
| |
| <p>We assume that the environment has been set up following the steps outlined in the <a href="../docs/edgent-getting-started">Getting started guide</a>. Let's begin by creating a <code>DirectProvider</code> and <code>Topology</code>. We also define the optimal temperature range.</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kn">import</span> <span class="nn">static</span> <span class="n">edgent</span><span class="o">.</span><span class="na">function</span><span class="o">.</span><span class="na">Functions</span><span class="o">.</span><span class="na">identity</span><span class="o">;</span> |
| |
| <span class="kn">import</span> <span class="nn">java.util.concurrent.TimeUnit</span><span class="o">;</span> |
| |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.analytics.sensors.Filters</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.analytics.sensors.Range</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.analytics.sensors.Ranges</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.providers.direct.DirectProvider</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.samples.utils.sensor.SimulatedTemperatureSensor</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.topology.TStream</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.topology.Topology</span><span class="o">;</span> |
| |
| <span class="kd">public</span> <span class="kd">class</span> <span class="nc">DetectValueOutOfRange</span> <span class="o">{</span> |
| <span class="cm">/** |
| * Optimal temperature range (in Fahrenheit) |
| */</span> |
| <span class="kd">static</span> <span class="kt">double</span> <span class="n">OPTIMAL_TEMP_LOW</span> <span class="o">=</span> <span class="mf">77.0</span><span class="o">;</span> |
| <span class="kd">static</span> <span class="kt">double</span> <span class="n">OPTIMAL_TEMP_HIGH</span> <span class="o">=</span> <span class="mf">91.0</span><span class="o">;</span> |
| <span class="kd">static</span> <span class="n">Range</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">optimalTempRange</span> <span class="o">=</span> <span class="n">Ranges</span><span class="o">.</span><span class="na">closed</span><span class="o">(</span><span class="n">OPTIMAL_TEMP_LOW</span><span class="o">,</span> <span class="n">OPTIMAL_TEMP_HIGH</span><span class="o">);</span> |
| |
| <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="n">main</span><span class="o">(</span><span class="n">String</span><span class="o">[]</span> <span class="n">args</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">Exception</span> <span class="o">{</span> |
| |
| <span class="n">DirectProvider</span> <span class="n">dp</span> <span class="o">=</span> <span class="k">new</span> <span class="n">DirectProvider</span><span class="o">();</span> |
| |
| <span class="n">Topology</span> <span class="n">top</span> <span class="o">=</span> <span class="n">dp</span><span class="o">.</span><span class="na">newTopology</span><span class="o">(</span><span class="s">"TemperatureSensor"</span><span class="o">);</span> |
| |
| <span class="c1">// The rest of the code pieces belong here</span> |
| <span class="o">}</span> |
| <span class="o">}</span> |
| </code></pre></div> |
| <h2 id="generating-temperature-sensor-readings">Generating temperature sensor readings</h2> |
| |
| <p>The next step is to simulate a stream of temperature readings using <a href="https://github.com/apache/incubator-edgent/blob/master/samples/utils/src/main/java/org/apache/edgent/samples/utils/sensor/SimulatedTemperatureSensor.java"><code>SimulatedTemperatureSensor</code></a>. By default, the sensor sets the initial temperature to 80°F and ensures that new readings are between 28°F and 112°F. In our <code>main()</code>, we use the <code>poll()</code> method to generate a flow of tuples, where a new tuple (temperature reading) arrives every second.</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="c1">// Generate a stream of temperature sensor readings</span> |
| <span class="n">SimulatedTemperatureSensor</span> <span class="n">tempSensor</span> <span class="o">=</span> <span class="k">new</span> <span class="n">SimulatedTemperatureSensor</span><span class="o">();</span> |
| <span class="n">TStream</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">temp</span> <span class="o">=</span> <span class="n">top</span><span class="o">.</span><span class="na">poll</span><span class="o">(</span><span class="n">tempSensor</span><span class="o">,</span> <span class="mi">1</span><span class="o">,</span> <span class="n">TimeUnit</span><span class="o">.</span><span class="na">SECONDS</span><span class="o">);</span> |
| </code></pre></div> |
| <h2 id="simple-filtering">Simple filtering</h2> |
| |
| <p>If the corn grower is interested in determining when the temperature is strictly out of the optimal range of 77°F and 91°F, a simple filter can be used. The <code>filter</code> method can be applied to <code>TStream</code> objects, where a filter predicate determines which tuples to keep for further processing. For its method declaration, refer to the <a href="/javadoc/latest/org/apache/edgent/topology/TStream.html#filter-org.apache.edgent.function.Predicate-">Javadoc</a>.</p> |
| |
| <p>In this case, we want to keep temperatures below the lower range value <em>or</em> above the upper range value. This is expressed in the filter predicate, which follows Java's syntax for <a href="https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html#syntax">lambda expressions</a>. Then, we terminate the stream (using <code>sink</code>) by printing out the warning to standard out. Note that <code>\u00b0</code> is the Unicode encoding for the degree (°) symbol.</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">TStream</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">simpleFiltered</span> <span class="o">=</span> <span class="n">temp</span><span class="o">.</span><span class="na">filter</span><span class="o">(</span><span class="n">tuple</span> <span class="o">-></span> |
| <span class="n">tuple</span> <span class="o"><</span> <span class="n">OPTIMAL_TEMP_LOW</span> <span class="o">||</span> <span class="n">tuple</span> <span class="o">></span> <span class="n">OPTIMAL_TEMP_HIGH</span><span class="o">);</span> |
| <span class="n">simpleFiltered</span><span class="o">.</span><span class="na">sink</span><span class="o">(</span><span class="n">tuple</span> <span class="o">-></span> <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Temperature is out of range! "</span> |
| <span class="o">+</span> <span class="s">"It is "</span> <span class="o">+</span> <span class="n">tuple</span> <span class="o">+</span> <span class="s">"\u00b0F!"</span><span class="o">));</span> |
| </code></pre></div> |
| <h2 id="deadband-filter">Deadband filter</h2> |
| |
| <p>Alternatively, a deadband filter can be used to glean more information about temperature changes, such as extracting the in-range temperature immediately after a reported out-of-range temperature. For example, large temperature fluctuations could be investigated more thoroughly.</p> |
| |
| <p>The <code>deadband</code> filter is a part of the <code>edgent.analytics</code> package focused on handling sensor data. Let's look more closely at the method declaration below.</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">deadband</span><span class="o">(</span><span class="n">TStream</span><span class="o"><</span><span class="n">T</span><span class="o">></span> <span class="n">stream</span><span class="o">,</span> <span class="n">Function</span><span class="o"><</span><span class="n">T</span><span class="o">,</span><span class="n">V</span><span class="o">></span> <span class="n">value</span><span class="o">,</span> <span class="n">Predicate</span><span class="o"><</span><span class="n">V</span><span class="o">></span> <span class="n">inBand</span><span class="o">)</span> |
| </code></pre></div> |
| <p>The first parameter is the stream to the filtered, which is <code>temp</code> in our scenario. The second parameter is the value to examine. Here, we use the <code>identity()</code> method to return a tuple on the stream. The last parameter is the predicate that defines the optimal range, that is, between 77°F and 91°F. it is important to note that this differs from the <code>TStream</code> version of <code>filter</code> in which one must explicitly specify the values that are out of range. The code snippet below demonstrates how the method call is pieced together. The <code>deadbandFiltered</code> stream contains temperature readings that follow the rules as described in the <a href="/javadoc/latest/org/apache/edgent/analytics/sensors/Filters.html#deadband-org.apache.edgent.topology.TStream-org.apache.edgent.function.Function-org.apache.edgent.function.Predicate-">Javadoc</a>:</p> |
| |
| <ul> |
| <li>the value is outside of the optimal range (deadband)</li> |
| <li>the first value inside the optimal range after a period being outside it</li> |
| <li>the first tuple</li> |
| </ul> |
| |
| <p>As with the simple filter, the stream is terminated by printing out the warnings.</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">TStream</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">deadbandFiltered</span> <span class="o">=</span> <span class="n">Filters</span><span class="o">.</span><span class="na">deadband</span><span class="o">(</span><span class="n">temp</span><span class="o">,</span> |
| <span class="n">identity</span><span class="o">(),</span> <span class="n">tuple</span> <span class="o">-></span> <span class="n">tuple</span> <span class="o">>=</span> <span class="n">OPTIMAL_TEMP_LOW</span> <span class="o">&&</span> <span class="n">tuple</span> <span class="o"><=</span> <span class="n">OPTIMAL_TEMP_HIGH</span><span class="o">);</span> |
| <span class="n">deadbandFiltered</span><span class="o">.</span><span class="na">sink</span><span class="o">(</span><span class="n">tuple</span> <span class="o">-></span> <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Temperature may not be "</span> |
| <span class="o">+</span> <span class="s">"optimal! It is "</span> <span class="o">+</span> <span class="n">tuple</span> <span class="o">+</span> <span class="s">"\u00b0F!"</span><span class="o">));</span> |
| </code></pre></div> |
| <p>We end our application by submitting the <code>Topology</code>.</p> |
| |
| <h2 id="observing-the-output">Observing the output</h2> |
| |
| <p>To see what the temperatures look like, we can print the stream to standard out.</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">temp</span><span class="o">.</span><span class="na">print</span><span class="o">();</span> |
| </code></pre></div> |
| <p>When the final application is run, the output looks something like the following:</p> |
| <div class="highlight"><pre><code class="language-" data-lang="">Temperature may not be optimal! It is 79.1°F! |
| 79.1 |
| 79.4 |
| 79.0 |
| 78.8 |
| 78.0 |
| 78.3 |
| 77.4 |
| Temperature is out of range! It is 76.5°F! |
| Temperature may not be optimal! It is 76.5°F! |
| 76.5 |
| Temperature may not be optimal! It is 77.5°F! |
| 77.5 |
| 77.1 |
| ... |
| </code></pre></div> |
| <p>Note that the deadband filter outputs a warning message for the very first temperature reading of 79.1°F. When the temperature falls to 76.5°F (which is outside the optimal range), both the simple filter and deadband filter print out a warning message. However, when the temperature returns to normal at 77.5°F, only the deadband filter prints out a message as it is the first value inside the optimal range after a period of being outside it.</p> |
| |
| <h2 id="range-values">Range values</h2> |
| |
| <p>Filtering against a range of values is such a common analytic activity that the <code>edgent.analytics.sensors.Range</code> class is provided to assist with that.</p> |
| |
| <p>Using a <code>Range</code> can simplify and clarify your application code and lessen mistakes that may occur when writing expressions to deal with ranges. Though not covered in this recipe, <code>Range</code>s offer additional conveniences for creating applications with external range specifications and adaptable filters.</p> |
| |
| <p>In the above examples, a single <code>Range</code> can be used in place of the two different expressions for the same logical range:</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">static</span> <span class="kt">double</span> <span class="n">OPTIMAL_TEMP_LOW</span> <span class="o">=</span> <span class="mf">77.0</span><span class="o">;</span> |
| <span class="kd">static</span> <span class="kt">double</span> <span class="n">OPTIMAL_TEMP_HIGH</span> <span class="o">=</span> <span class="mf">91.0</span><span class="o">;</span> |
| <span class="kd">static</span> <span class="n">Range</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">optimalTempRange</span> <span class="o">=</span> <span class="n">Ranges</span><span class="o">.</span><span class="na">closed</span><span class="o">(</span><span class="n">OPTIMAL_TEMP_LOW</span><span class="o">,</span> <span class="n">OPTIMAL_TEMP_HIGH</span><span class="o">);</span> |
| </code></pre></div> |
| <p>Using <code>optimalTempRange</code> in the Simple filter example code:</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">TStream</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">simpleFiltered</span> <span class="o">=</span> <span class="n">temp</span><span class="o">.</span><span class="na">filter</span><span class="o">(</span><span class="n">tuple</span> <span class="o">-></span> |
| <span class="o">!</span><span class="n">optimalTempRange</span><span class="o">.</span><span class="na">contains</span><span class="o">(</span><span class="n">tuple</span><span class="o">));</span> |
| </code></pre></div> |
| <p>Using <code>optimalTempRange</code> in the Deadband filter example code:</p> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">TStream</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">deadbandFiltered</span> <span class="o">=</span> <span class="n">Filters</span><span class="o">.</span><span class="na">deadband</span><span class="o">(</span><span class="n">temp</span><span class="o">,</span> |
| <span class="n">identity</span><span class="o">(),</span> <span class="n">optimalTempRange</span><span class="o">);</span> |
| </code></pre></div> |
| <h2 id="the-final-application">The final application</h2> |
| <div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kn">import</span> <span class="nn">static</span> <span class="n">edgent</span><span class="o">.</span><span class="na">function</span><span class="o">.</span><span class="na">Functions</span><span class="o">.</span><span class="na">identity</span><span class="o">;</span> |
| |
| <span class="kn">import</span> <span class="nn">java.util.concurrent.TimeUnit</span><span class="o">;</span> |
| |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.analytics.sensors.Filters</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.analytics.sensors.Range</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.analytics.sensors.Ranges</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.providers.direct.DirectProvider</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.samples.utils.sensor.SimulatedTemperatureSensor</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.topology.TStream</span><span class="o">;</span> |
| <span class="kn">import</span> <span class="nn">org.apache.edgent.topology.Topology</span><span class="o">;</span> |
| |
| <span class="cm">/** |
| * Detect a sensor value out of expected range. |
| */</span> |
| <span class="kd">public</span> <span class="kd">class</span> <span class="nc">DetectValueOutOfRange</span> <span class="o">{</span> |
| <span class="cm">/** |
| * Optimal temperature range (in Fahrenheit) |
| */</span> |
| <span class="kd">static</span> <span class="kt">double</span> <span class="n">OPTIMAL_TEMP_LOW</span> <span class="o">=</span> <span class="mf">77.0</span><span class="o">;</span> |
| <span class="kd">static</span> <span class="kt">double</span> <span class="n">OPTIMAL_TEMP_HIGH</span> <span class="o">=</span> <span class="mf">91.0</span><span class="o">;</span> |
| <span class="kd">static</span> <span class="n">Range</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">optimalTempRange</span> <span class="o">=</span> <span class="n">Ranges</span><span class="o">.</span><span class="na">closed</span><span class="o">(</span><span class="n">OPTIMAL_TEMP_LOW</span><span class="o">,</span> <span class="n">OPTIMAL_TEMP_HIGH</span><span class="o">);</span> |
| |
| <span class="cm">/** |
| * Polls a simulated temperature sensor to periodically obtain |
| * temperature readings (in Fahrenheit). Use a simple filter |
| * and a deadband filter to determine when the temperature |
| * is out of the optimal range. |
| */</span> |
| <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="n">main</span><span class="o">(</span><span class="n">String</span><span class="o">[]</span> <span class="n">args</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">Exception</span> <span class="o">{</span> |
| |
| <span class="n">DirectProvider</span> <span class="n">dp</span> <span class="o">=</span> <span class="k">new</span> <span class="n">DirectProvider</span><span class="o">();</span> |
| |
| <span class="n">Topology</span> <span class="n">top</span> <span class="o">=</span> <span class="n">dp</span><span class="o">.</span><span class="na">newTopology</span><span class="o">(</span><span class="s">"TemperatureSensor"</span><span class="o">);</span> |
| |
| <span class="c1">// Generate a stream of temperature sensor readings</span> |
| <span class="n">SimulatedTemperatureSensor</span> <span class="n">tempSensor</span> <span class="o">=</span> <span class="k">new</span> <span class="n">SimulatedTemperatureSensor</span><span class="o">();</span> |
| <span class="n">TStream</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">temp</span> <span class="o">=</span> <span class="n">top</span><span class="o">.</span><span class="na">poll</span><span class="o">(</span><span class="n">tempSensor</span><span class="o">,</span> <span class="mi">1</span><span class="o">,</span> <span class="n">TimeUnit</span><span class="o">.</span><span class="na">SECONDS</span><span class="o">);</span> |
| |
| <span class="c1">// Simple filter: Perform analytics on sensor readings to</span> |
| <span class="c1">// detect when the temperature is completely out of the</span> |
| <span class="c1">// optimal range and generate warnings</span> |
| <span class="n">TStream</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">simpleFiltered</span> <span class="o">=</span> <span class="n">temp</span><span class="o">.</span><span class="na">filter</span><span class="o">(</span><span class="n">tuple</span> <span class="o">-></span> |
| <span class="o">!</span><span class="n">optimalTempRange</span><span class="o">.</span><span class="na">contains</span><span class="o">(</span><span class="n">tuple</span><span class="o">));</span> |
| <span class="n">simpleFiltered</span><span class="o">.</span><span class="na">sink</span><span class="o">(</span><span class="n">tuple</span> <span class="o">-></span> <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Temperature is out of range! "</span> |
| <span class="o">+</span> <span class="s">"It is "</span> <span class="o">+</span> <span class="n">tuple</span> <span class="o">+</span> <span class="s">"\u00b0F!"</span><span class="o">));</span> |
| |
| <span class="c1">// Deadband filter: Perform analytics on sensor readings to</span> |
| <span class="c1">// output the first temperature, and to generate warnings</span> |
| <span class="c1">// when the temperature is out of the optimal range and</span> |
| <span class="c1">// when it returns to normal</span> |
| <span class="n">TStream</span><span class="o"><</span><span class="n">Double</span><span class="o">></span> <span class="n">deadbandFiltered</span> <span class="o">=</span> <span class="n">Filters</span><span class="o">.</span><span class="na">deadband</span><span class="o">(</span><span class="n">temp</span><span class="o">,</span> |
| <span class="n">identity</span><span class="o">(),</span> <span class="n">optimalTempRange</span><span class="o">);</span> |
| <span class="n">deadbandFiltered</span><span class="o">.</span><span class="na">sink</span><span class="o">(</span><span class="n">tuple</span> <span class="o">-></span> <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Temperature may not be "</span> |
| <span class="o">+</span> <span class="s">"optimal! It is "</span> <span class="o">+</span> <span class="n">tuple</span> <span class="o">+</span> <span class="s">"\u00b0F!"</span><span class="o">));</span> |
| |
| <span class="c1">// See what the temperatures look like</span> |
| <span class="n">temp</span><span class="o">.</span><span class="na">print</span><span class="o">();</span> |
| |
| <span class="n">dp</span><span class="o">.</span><span class="na">submit</span><span class="o">(</span><span class="n">top</span><span class="o">);</span> |
| <span class="o">}</span> |
| <span class="o">}</span> |
| </code></pre></div> |
| |
| <div class="tags"> |
| |
| </div> |
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