Passing string as function argument

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Maximilian 2011-11-24

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Hey. I am having a little difficulty with processing a large batch of data. I have approximately 1700 independent data points in my workspace. I would like to scale each of those with respect to a factor. Each variable is 1024*2 with the name something like spec100_0.

If I use a = who to list all variables, I can access each string by a{i,1} = (variablename)

Is there a way to use a{i,1} with a counter to pass all variables through a function? At the moment when i do that I only get the string but not the associated variable.

Thanks for any help.

Max

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David Young 2011-11-24

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It's a bad idea to store your data in 1700 different variables: you'll find it is inefficient, and you already see how awkward it makes your code. It's far far better to use an array with 1700 elements. See this article.

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Sven 2011-11-24

Need to scale by two different amounts for the two columns? Also easy:

[myData(:,1,:)*5 myData(:,2,:)*10]

There's also a slightly cleaner version with a little more advanced syntax:

bsxfun(@times, myData, [5 10])

Maximilian 2011-11-24

done the entire thing within 15min. Spent hours trying to get it to work. Learn something new every day!

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Andrei Caragea 2011-11-24

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Yes you can, with the eval function. Let me give you an example. Say you havein your workspace 3 variables: A, B, S, where A and B are doubles (matrices with numbers basically) and S is a cell like S={'A';'B'}. Then S(1)='A' and eval(S{1})=content of A (for example [1 2;3 4]). So now if f is your function, just do for i=1:2 f(eval(S{i})) end.