How to convert a string to array or matrix?

Hi everyone, I want to convert a string '[2:0.5:4]' to an array. Thanks in advance.

Answer 1

[Walter Roberson]

With those quotation marks, it is already an array -- a character vector.

Perhaps you want it expanded into the numeric matrix [2 2.5 3 3.5 4] ?

If so, the easiest way is to use str2num() on it. That will eval() the string. If you had total control over what went into the string, and if you are not doing code generation, then that can be enough.

If you are doing code generation or if you do not have total control of the string, then you can:

fmt1 = '[%f:%f:%f]';
fmt2 = '%f:%f:%f'
parts = sscanf(TheString, fmt1);
if isempty(parts)
  parts = sscanf(TheString, fmt2);
end
if length(parts) < 2
  error('Sorry, that is not a range I recognize')
end
if length(parts) == 2
  range = parts(1) : parts(2);
else
  range = parts(1) : parts(2) : parts(3);
end

[Thuan Nguyen]

May I have one more question? I'm having a variable a = 'x.^2+y.^2'. How can I use a in "@(x,y)" anonymous function?

a='x.^2+y.^2'
z=@(x,y)a

[Walter Roberson]

str2func(['@(x,y)' a])

[Walter Roberson]

Again if you do not have total control over the string then this is dangerous. Suppose the user had entered delete('*.*')