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Using a string as a command?

Asked by Kavan on 7 Mar 2013

Let's say I have x=linspace(0,10), and y='x.^2', as a string. How do I tell MatLab to apply y to x? What I am asking is, in the command window, I can type yy=x.^2 to get the desired result. But, I am writing a script and I need to be able to take the string 'x.^2' and tell MatLab yy=x.^2, so I get a yy double that I can plot in the linspace I created. However, simply typing yy=y just creates another string yy='x.^2'.

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Kavan

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3 Answers

Answer by Jing on 7 Mar 2013

You can do that by using 'eval'. When y is the string, try the following command.

yy=eval(y);

2 Comments

Walter Roberson on 7 Mar 2013

This is not recommended.

Jing on 8 Mar 2013

Why not?

Jing
Answer by Andrei Bobrov on 7 Mar 2013
Edited by Andrei Bobrov on 7 Mar 2013

eg:

str = 'x.^2';
yy = str2func(['@(',char(symvar(str)),')',str]);

use

x = 0:10;
out = yy(x);

ADD

str = 'x^2 - y^2'
k = strcat(symvar(str),',');
k = [k{:}];
yy = str2func(['@(',k(1:end-1),')',vectorize(str)]);

use

x = 1:10;
y = linspace(5,20,10);
out = yy(x,y);

1 Comment

Andrei Bobrov
Answer by Walter Roberson on 7 Mar 2013
f = str2func( ['@(x) ' TheString] );
yy = f(x);

0 Comments

Walter Roberson

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