Scilab/C2/Plotting-2D-graphs/English
From Script | Spoken-Tutorial
Title of script: Plotting 2D Graphs
Author: Anuradha Amrutkar
Keywords: Plotting, 2D Graphs, plot, plot2d
| |
|
|---|---|
| Slide | Welcome to the spoken tutorial on Plotting 2D graphs with scilab. |
| Slide | Assuming that Scilab is installed on your computer, we will discuss plots in Scilab. |
| Narration | Scilab offers many ways to create and customize various types of 2D and 3D plots. |
| Narration | The several common charts Scilab can create are: x-y plots, contour plots, 3D plots, histograms, bar charts, etc... |
| Demonstration | Now open your Scilab console window. |
| Demonstration | I will use Plotting.sce file to cut and paste the commands. |
| Narration | In order to Plot, we need a set of points. Let us create a sequence of equally spaced points. |
| Narration | This can be done by the linspace command which creates a linearly equally spaced vector. |
| Demonstration | For Example
--> x=linspace(1,10,5) x is a row vector with 5 points with linearly equally spaced between 1 and 10 |
| Demonstration | Similarly y is a row vector with linearly equally spaced 5 points between 1 and 20
--> y=linspace(1,20,5); |
| Narration | More information on linspace command can be obtained from the Help documentation. |
| Narration | We will now plot a graph with the arguments x and y using the Plot function. |
| Demonstration | This is similar to the one used in matlab.
--> plot(x,y) creates a graph of x verses y as you see. |
| Demonstration | Notice that the graphics window is labeled as '0' We will open another graphic window using the
xset('window',1)
function. I will close this cut the xset function paste in scilab hit enter. |
| Demonstration | You will see a graphic window number 1. Note that two arguments are passed to this function namely the window and 1. |
| Demonstration | The next graph will be plotted on this window. |
| Demonstration | For scilab plot 2d is the native function used to plot 2d graphs.
--> plot2d(x,y,style=3) |
| Demonstration | plot2d command plots a graph of x verses y as you see. |
| Demonstration | Notice that there is a third argument called style. |
| Narration | Style argument is optional.It is used to customize the appearance of the plot. |
| Demonstration | For positive values of style the curve is a plain with different colours like green for 3 in our case. |
| Narration | The default value of style is 1. |
| Narration | Try plotting graphs for negative values and see the difference in appearance for yourself. |
| Demonstration | Also we can set the start points and end points for x and y axis by passing the fourth argument.It is called rect.
--> plot2d(x,y,style=3,rect=[1,1,10,20]) |
| Demonstration | We have x axis starting from 1 to 10 and y axis from 1 to 20. |
| Narration | The order of argument in the rect command is xmin,ymin,xmax and ymax. |
| Narration | Let us now learn about Title,Axis and Legends |
| Demonstration | To configure labels to the axis and title to the plot we can use the commands
--> title("My title")
--> xlabel("X"); and
--> ylabel("Y");
|
| Demonstration | I will cut this set of commands and paste in the console. Hit enter |
| Demonstration | 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. |
| Demonstration | You may want to configure the title and axis of the plot in a single command instead of 3 for this purpose we use the xtitle
--> xtitle ( " My title " , " X axis " , " Y axis " ); command with all the 3 arguments. |
| Demonstration | I will cut this command paste in scilab enter. |
| Narration | Now you see that the x axis label is X axis , Y axis and the title is My title. |
| Demonstration | The clf() function that i am typing now will clear the graphic window as you see. |
| Narration | It is useful while plotting different graph on the same graphic window. |
| Demonstration | I will close this window. |
| Narration | 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. |
| Narration | Let us see an example for this I will scroll down |
| Demonstration | We will define the x axis points in a row vector x using the linspace command |
| Demonstration | Let us define a function
y1 = x^2 plot x verses y1 |
| Demonstration | define another function
y2 = 2*x^2 plot x verses y2 |
| Demonstration | we will also give label and title to our graph |
| Demonstration | Notice that we have additionally passed ”o-” and ”+-” commands to the plot function, to change the appearance of the curve |
| Demonstration | --> x = linspace ( 1 , 10 , 50 );
--> y1 = x^2;
--> plot (x ,y1 , "o-")
--> y2 = 2*x ^2;
--> plot (x, y2, "+-")
--> xtitle ("My title" , "X axis" , "Y axis" );
|
| Demonstration | These arguments are not a part of the plot2d function. |
| Narration | They can be used only with the plot function |
| Demonstration | I will copy these set of commands and paste in the scilab console. |
| Demonstration | You see the graph |
| Narration | Wouldn't it be of great help to know which curve is associated with which function? |
| Demonstration | This can be achieved using the legend command as you see
--> legend ( " x ^ 2 " , " 2* x ^ 2 " ); |
| Demonstration | "o-" curve represents function y1=x^2 function and "+-" curve represents function y2=2*x^2 |
| Demonstration | I will close this graphic window |
| [[[ File:title.jpeg]]] | |
| Narration | We will now discuss about plot2d demos and subplot function |
| Narration | Scilab provides demos for all its major functions Demos of plot2d can be viewed through demonstration tab. |
| Demonstration | click on Graphics,click plot2d_3d plots and select a demo out the various demos provided. I will click on plot2d. |
| Demonstration | You will see the demo graph |
| Demonstration | The code for this graph can also be seen by clicking the view code button here. |
| Narration | This link does not open in Mac OS but works in windows and linux |
| Demonstration | Nevertheless in Mac the code can be viewed through the directory. |
| Demonstration | Let us go to the terminal. |
| Demonstration | currently i am in demos directory of scilab 5.2 |
| Demonstration | The full path to this directory is shown here. |
| Demonstration | we will type
ls to see the list of demos available as you see here. |
| Demonstration | then we will select the 2d_3d_plots directory and hit enter type ls again to see various demo code available in the sce files |
| Demonstration | we will view the code for the demo which we have seen earlier. type and hit enter.
more plot2d.dem.sce |
| Demonstration | Here you will see the code for the demo graph of plot2d function |
| Demonstration | I will close the terminal I will close the demo graph and the demos window |
| Demonstration | Similarly you can go through the other demos and explore scilab |
| Narration | Let us now discuss about Subplot function |
| Narration | The subplot() function divides a graphics window into a matrix of sub-windows. |
| Narration | To explain this function we will use demos for plotting 2D graphs in scilab. |
| Demonstration | for eg. type
-->plot2d() in your console and see the demo plot for this function |
| [[[ File:plot2d.jpg]]] | |
| Demonstration | I will close this window. |
| Narration | 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 the third argument denotes the current window in which the plot will be plotted |
| Demonstration | I will execute this whole set of commands by copying in the scilab console |
| Demonstration | -->subplot(221)
-->plot2d() -->subplot(222) -->plot2d2() -->subplot(2,2,3) -->plot2d3() -->subplot(2,2,4) -->plot2d4() |
| Demonstration | [[[ File:subplot2.GIF]]] |
| Demonstration | You can see 4 plots in a single plot window |
| Demonstration | The plot obtained can be saved as a image on your computer |
| Demonstration | Click on the graphic window, go to File menu select export to . |
| Demonstration | Give a suitable title to your plot, select a destination folder to save your file select the file format in which you want your image to appear. |
| Demonstration | I will select the JPEG format and Click Save. |
| Demonstration | Browse through the directory to open the image and verify yourself whether it has been saved or not. |
| Narration | This brings us to the end of this spoken tutorial on Plotting in Scilab. |
| Slide | There are many other functions in Scilab which will be covered in other spoken tutorials. |
| Slide | Keep watching the Scilab links. |
| Slide | Spoken Tutorials are part of the Talk to a Teacher project, supported by the National Mission on Education through ICT. |
| Slide | More information on the same is available at http://spoken-tutorial.org/NMEICT-Intro. |
