Call variables in for loop

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Rok mr 2012-3-22

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采纳的回答： Kevin Holst

Hi to all,

L1=4 L2=3 ... L30=12

for i=1:30 P(:,i)=sprintf(L%1d,i) - sprintf(L%1d,i+1) end

The result should be P(1)=L1-L2, P(2)=L2-L3, P(3)=L3-L4, P(4)=L4-L5 but it's not :) What should I use instead sprintf?

Thank you for you answers!!!

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Kevin Holst 2012-3-22

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To do this like you're attempting requires the use of the eval function, but be very careful in its use. Google 'eval matlab' for more information on why. And actually, the way you've got it set up wouldn't work. Your for loop needs to run from 1:29 because there's no L31.

for i = 1:29
  eval(['P(' num2str(i) ')=L' num2str(i) '-L' num2str(i+1) ';'])
end

Is there any reason why your L variables aren't in a single L vector?

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Kevin Holst 2012-3-22

@Oleg, I haven't tried the eval(eval(eval(... suggestion, but I did evaluate char([102 108 105 112 108 114 40 39 116 105 120 101 39 41]) in my workspace... very sneaky! ;) That's the nice way to show a problem with eval. The mean way would be to "accidentally" have someone recursively remove all of the contents of their hard drive. That'd be a bad day.