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Scilab 2D plots

This is a brief introduction to the great potential of Scilab’s graphic capabilities. We’ll review a few of the basic commands and operations to carry out this important task in sofisticated software like Scilab or Scicoslab.


Simple Graphic Representation

In a simple graphic representation we just need two vectors with the same number of elements. The idea is to show a mathematical relationship or function that results in a 2D graph. The built-in functions that allow us to do that are plot and plot2d.

The following functions are quite compatible with Matlab:

  • plot
  • subplot
  • xlabel
  • ylabel
  • legend
  • title

These functions are different from the Matlab ones:

  • xdel(n) – deletes a figure window
  • scf(n) – opens a figure window
  • xgrid – shows a grid on the plot
  • ax = get("current_axes"); ax.data_bounds = [xL, yL; xU, yU]; - it’s an approximation of the Matlab axis function


This code

x = -10 : .1 : 10; / our independent values
y = cos(x) .* x; / define our dependent values
plot(x, y) / both vectors

xlabel('x'); ylabel('y'); / define labels
legend('y = cos(x) * x'); / define legend
title('My First Scilab 2D Plot') / title


produces this Scilab plot

Scilab 2D plots - basic functions

We can re-define the axis values and add a grid by adding these lines to the previous code:

/ the handle of the newly created axes
ax = get("current_axes");

/ axes
ax.data_bounds = [-10, -6; 10, 8];

/ grid
xgrid


The resulting plot is

Scilab grid and bounded axes


To erase the contents of one figure window, you only need to type the command clf in the command line, or you can select Erase Figure in the edit menu of the figure selected.

If you want to generate new plots without removing the previous one, it’s necessary to indicate the creation of a new one using the command ‘scf’, whose syntax is scf(integer number of the new plot).

If you run the code below

x = -10 : .1 : 10; / define our independent values
y = cos(x) .* x; / our dependent values
y2 = 3 * sin(x); / another function
plot(x, y,'b', x, y2, 'r')

xlabel('x'); ylabel('y'); / define labels
legend('y = cos(x) * x', 'y2 = 3 sin(x)'); / define legend

you can see two lines in the same window, each with a different legend and color


Scilab - two functions in one window


From 'Scilab 2D Plots' to Matlab home

From 'Scilab 2D Plots' to Scilab


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