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Tutorial 8. Series Functions - Part I

In this tutorial, we will learn about data processing via series functions. It is recommended that you read the topic Series Functions before continue.

The Basics

Start the DataScene program and create an empty project with an empty data table, Table 1. For rows 1 to 101 of Table 1, set two column formulas "(Row - 1) * (2 * PI) / 100" and "COS(CELL(1))" for Column 1 and Column 2, respectively. Plot a Line series with Column 1 as the Position component and Column 2 as the Value component. Select the graph document, Graph 1, as the active document. You should see a Line series, line1, representing the y=cos(x) function in the [0, 2p] range.

Select the Graph: Series Function: Integration menu command to open the Series Function dialog box. In the dialog box, check the Generate Data Table check box and then click the Apply button on the dialog box to apply the Integrate series function on line1. DataScene calculates the series function and plot the destination series line2 in the same graph as the source series line1. DataScene also generates a data table called Table2(line2: Integrate) to contain the data of the destination series line2. Close the Series Function dialog box. As we expect, the destination line2 series is a line of the sine function.

Fig. 1. line2 is the destination series of the Integrate series function of line1.

 

Select line2 as the active series and then select the Graph: Series Function: Edit Function producing line 2 menu command to open the Series Function dialog box. Switch to the Domain tab-page of the dialog box, uncheck the Always include all data check box and then start to change the values of the Minimum and Maximum track bars. You will see two dashed lines are drawn in the graph indicating the changing series function domain. Click the Apply button to apply the new domain and note how line2 changes to respond to the new domain.

Re-check the Always include all data check box to use all data points of line1 in the series function and then click the Apply button. Switch back to the Function tab-page of the Series Function dialog box and then select Add in the Function Type combo-box and check the Create New Function radio box. DataScene refreshes the two list boxes in the Function Source group box. Move both line1 and line2 from the Available list box to the Selected list box by clicking inside the Available list box and then clicking the button. The dialog box should look like that shown in Fig. 2. Click the Apply button to apply the Add series function on the source series line1 and line2 and produce the destination series, line3, in the same graph as the source series.

Fig. 2. Applying the Add series function of line1 and line2 in the Series Function dialog box.

 

Close the Series Function dialog box by clicking its Close button. Change the color of line3 to green so that it is more visible. Select Table 1 as the active document, change the column formula on Column 2 to "COS(2 * COL(1))" and apply it. Switch back to Graph 1, you will see that line2 and line3 have been recalculated automatically in accordance with the new data in line1.

Fig. 3. line2 and line3 have been recalculated due to the change of line1.

 

Now that we have seen how to apply series functions to source series that have only two mandatory series components, we will demonstrate applying series functions to source series with more than two mandatory series components in the following example.

Close the active project without saving it. Open the file Examples\Sample Graph\Candle.dts in the DataScene installation folder (which can be opened by selecting the Help: Demo Projects menu command). Select graph Candle and change the view dimension to 2D. Execute the Graph: Series Function: Cubic Spline menu command. On the Series Function dialog box click the Apply button - a new Line series is produced by cubic-spline interpolation using values in the Close component of candle1. Click candle1 in the Selected list box in the Function Source group box. DataScene adds the Value combo-box to the Function Source group box and selects Close as its value, indicating the Close series component of candle1 is used as the value component of the cubic spline series function.

Fig. 4. Selecting the Value component for the source series in the Series Function dialog box.

 

In the Series Function dialog box, select different values in the Value combo-box and then click the Apply button. You will see the destination Line series change as the values in the Value combo-box change. After you finish, close the project without saving it.

FFT Filter

In this section, we will show more utilities of the Series Function dialog box via an example of the FFT Filter series function.

Create an empty project and add to it an empty data table, Table 1. For rows 1 to 101 of Table 1, set two column formulas "(Row - 1) * (2 * PI) / 100" and "COS(COL(1)) + SIN(2 * COL(1)) + RND() / 4" for Column 1 and Column 2, respectively. Plot a Line series, line1, with Column 1 as the Position component and Column 2 as the Value component, respectively.

Select the Series Function: FFT Filter menu command to open the Series Function dialog box. Switch to the FFT Filter tab-page of the dialog box, select Band Filter in the Filter Type combo-box. DataScene adds to the dialog box a tab-page called Band Filter and automatically switches to it. Click the Apply button on the dialog box to generate the destination Line series, line2, which is plotted in the same graph as line1. Note that the Messages Window springs out with information about the filter function and the built-in freq variable. Now increase the value in the Lower Factor spin box and observe how the filter function changes (as shown in the Messages Window) and how line2 changes - in this case we created a high-pass band filter. Restore the Lower Factor to 0 and begin to decrease the value in the Upper Factor spin box and observe the changes of the filter function and line2 - in this second case we created a low-pass band filter.

Fig. 5. A low-pass band filter on line1 producing line2. The cutoff is 0.08 Nyquist fresuency (7.96 Hz).

 

Next we will apply a Gaussian filter function. Switch to the FFT Filter tab-page of the Series Function dialog box and select User Defined in the Filter Type combo-box. Click the Editor button to open the Formula Editor. With the Functions selected in the Library Mode, browse to VOIGT() in the Library text box and double click it to insert it into the formula. Select Variables & Parameters in the Library Mode and then double click freq in the Library to insert it into the formula. Start typing in the Formula text box and change the formula to "VOIGT(freq - 0.08, 0.02, 0)" - this is a Gaussian function with center value of 0.08 and variance of 0.02 (refer to the description of the VOIGT function in the Description text box). Click the OK button of the Formula Editor. Click the Apply button and then the Close button to close the Series Function dialog box.

Fig. 6. A Gaussian FFT filter applied to line1 produces line2.

 

Close the opened project without saving it.

     

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