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Revision as of 18:01, 4 October 2017

Time Narration
00:00 Welcome to the spoken tutorial on Plotting 2D graphs with Scilab.
00:04 Assuming that Scilab is installed on your computer, we will discuss plots in Scilab.
00:10 Scilab offers many ways to create and customize various types of 2D and 3D plots.
00:15 The several common charts Scilab can create are: x-y plots, contour plots, 3D plots, histograms, bar charts etc...
00:24 Now open your Scilab console window.
00:28 I will use Plotting.sce file to cut and paste the commands.
00:34 In order to plot, we need a set of points. Let us create a sequence of equally spaced points.
00:39 This can be done by the linspace command which creates a linearly equally spaced vector.
00:45 For Example,
00:48 x is a row vector with 5 points linearly equally spaced between 1 and 10.
00:57 Similarly y is a row vector with linearly equally spaced 5 points between 1 and 20.
01:08 More information on linspace can be obtained from the Help documentation.
01:14 We will now plot a graph with the arguments x and y using the plot function.
01:19 This is similar to the one used in matlab.
01:23 plot(x,y) creates a graph of x verses y as you see.
01:31 Notice that the Graphics window is labeled as '0'.
01:36 We will open another graphic window using the xset function.
01:41 I will close this.
01:43 Cut the xset function, paste in Scilab, hit Enter.
01:50 You will see a Graphic window number 1.
01:54 Note that two arguments are passed to this function namely the 'window' and 1.
02:03 The next graph will be plotted on this window.
02:06 For Scilab, plot2d is the native function used to plot 2d graphs.
02:14 plot2d command plots a graph of x verses y as you see.
02:26 Notice that there is a third argument called 'style'.
02:31 style argument is optional. It is used to customize the appearance of the plot.
02:36 For positive values of style, the curve is plain with different colours like green for 3 in our case.
02:44 The default value of style is 1.
02:46 Try plotting graphs for negative values and see the difference in appearance yourself.
02:51 Also we can set the start points and end points for x and y axes by passing the fourth argument.
02:57 It is called rect. As you see,
03:07 we have x axis starting from 1 to 10 and y axis from 1 to 20.
03:14 The order of argument in the rect command is xmin, ymin, xmax and ymax.
03:24 Let us now learn about title, axis and legends.
03:28 To configure labels to the axis and title to the plot we can use the commands title, xlabel and ylabel.
03:38 I will cut this set of commands and paste in the console. Hit Enter.
03:45 You will see that the graph has been labeled x to the x-axis, y to the y-axis and the title of the graph is 'My title'.
03:58 You may want to configure the title and axes of the plot in a single command instead of 3
04:04 For this purpose we use the xtitle command with all the 3 arguments.
04:11 I will cut this command, paste in scilab, Enter.
04:18 Now you see that the x axis label is X axis , Y axis and the title is 'My title'.
04:26 The clf() function that I am typing now, will clear the graphic window as you see.
04:36 It is useful while plotting different graphs on the same graphic window.
04:41 I will close this window.
04:44 Sometimes we need to compare two sets of data in the same plot, that is, 1- set of x data and 2- set of y data.
04:51 Let us see an example for this, I will scroll down.
04:56 We will define the x-axis points in a row vector x using the linspace command.
05:03 Let us define a function
05:05 y1 = x square.
05:07 plot x verses y1.
05:10 Define another function y2 = 2 x square.
05:15 plot x verses y2.
05:17 We will also give label and title to our graph.
05:22 Notice that we have additionally passed ”o-” and ”+ -” commands to the plot function, to change the appearance of the curve.
05:33 These arguments are not a part of the plot2d function.
05:37 They can be used only with the plot function.
05:41 I will copy these set of commands and paste in the Scilab console.
05:49 You see the graph.
05:51 Wouldn't it be of great help to know which curve is associated with which function?
05:56 This can be achieved using the legend command as you see.
06:08 "o-" curve represents function y1=x square and "+-" curve represents function y2=2*x^2 (y2=2x square)
06:19 I will close this graphic window.
06:22 We will now discuss about plot2d demos and subplot function.
06:28 Scilab provides demos for all its major functions.
06:31 Demos of plot2d can be viewed through the demonstration tab.
06:39 Click on Graphics, click 2D and 3D plots and select a demo out of the various demos provided.
06:51 I will click on plot2d.
06:54 You will see the demo graph.
06:55 The code for this graph can also be seen by clicking on the view code button here.
07:02 This link does not open in Mac OS but it works in Windows and Linux.
07:07 Never the less in Mac the code can be viewed through the directory.
07:12 Let us go to the terminal.
07:15 Currently I am in 'demos' directory of Scilab 5.2 as shown.
07:21 The full path to this directory is shown here.
07:27 We will type ls to see the list of demos available, as you see here.
07:36 Then we will select the 2d_3d_plots directory and hit Enter.
07:46 Type ls again to see the various demo code available in the 'sce' files.
07:55 We will view the code for the demo which we have seen earlier.
08:00 Type more plot2d.dem.sce and hit Enter.
08:11 Here you will see the code for the demo graph of plot2d function.
08:18 I will close the terminal.
08:21 I will close the demo graph and the demo window.
08:26 Similarly you can go through the other demos and explore Scilab.
08:29 Let us now discuss about subplot function.
08:33 The subplot() function divides the graphics window into a matrix of sub-windows.
08:37 To explain this function we will use demos for plotting 2D graphs in Scilab.
08:43 For example, type plot2d in your console and see the demo plot for this function.
08:58 I will close this window.
09:00 The subplot command breaks the graphics window into a '2 by 2' matrix of sub-windows represented by the first two arguments in the subplot command.
09:10 The third argument denotes the current window in which the plot will be plotted.
09:15 I will execute this whole set of commands by copying it to the scilab console.
09:24 You can see 4 plots in a single plot window .
09:28 The plot obtained can be saved as an image on your computer.
09:32 Click on the graphic window, go to File menu, select Export to .
09:39 Give a suitable title to your plot.
09:50 Select a destination folder to save your file.
09:54 Select the file format in which you want your image to appear.
09:59 I will select the JPEG format and click Save.
10:05 Browse through the directory to open the image and verify yourself whether it has been saved or not.
10:11 This brings us to the end of this spoken tutorial on Plotting in Scilab.
10:15 There are many other functions in Scilab which will be covered in other spoken tutorials.
10:20 Keep watching the Scilab links.
10:22 Spoken Tutorials are part of the Talk to a Teacher project, supported by the National Mission on Education through ICT.
10:29 More information on the same is available on the following link.
10:32 Thanks for joining. Good bye.

Contributors and Content Editors

Gaurav, Krupali, PoojaMoolya, Sandhya.np14, Sneha