Scilab/C2/Plotting-2D-graphs/English-timed
From Script | Spoken-Tutorial
| 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, one set of x data and two sets 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. |
