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Fast way to replace elements in a matrix?

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Salad Box
Salad Box 2019-1-29
评论： madhan ravi 2019-1-29
Hi,
for eample I have an a matrix
a =
245 255 255
254 252 255
251 250 239
rules:
find the row index where all 3 numbers in the row are greater than 250.
Is there a faster way to achieve it than do it in a loop?
  2 个评论
Stephen23
Stephen23 2019-1-29
编辑：Stephen23 2019-1-29
Note that the question specifically asks for "Fast way to replace elements in a matrix?", and in real code (not just an assignment) logical indexing would likely be used as it avoids the find call:
https://www.mathworks.com/help/matlab/math/array-indexing.html
madhan ravi
madhan ravi 2019-1-29
Agree with Stephen , I used find() to explicitly show which row it was.

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madhan ravi
madhan ravi 2019-1-29
编辑：madhan ravi 2019-1-29
idx=all(a>250,2) % logical index
L_idx=find(idx) % linear index , gives row number

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