How can I change (or not change) the value of a variable each iteration?

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Stephanie Diaz 2017-5-26

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https://ww2.mathworks.cn/matlabcentral/answers/342137-how-can-i-change-or-not-change-the-value-of-a-variable-each-iteration

评论： Walter Roberson 2017-5-31

Hi,

I am attempting to either change the value of a variable each iteration, or keep the value the same, depending on the circumstances. I have a loop of 24 iterations,where I am selecting elements from a matrix (X) according to a set of criteria. It is set up something like the following:

X=matrix
xpos=100 %initial x- position
ypos=100 %initial y- position
    for t=1:24
        hour = t
        trip_duration = t
     for ii=1:10
      for jj=1:10
        if X(xpos+ii,ypos+jj) = 0
           trip_duration  = 1
        end
       end
     end
  end

Basically, the variable "trip_duration" resets to "1" every time an element with a value of "0" is found. The idea is for trip duration to then be "2" in the next iteration. If no element with a value of 0 is found, then trip-duration is simply "t". So, at any point in the loop, trip_duration and t can have different values, or the same. I've tried several ways to represent this, but am not successful in having trip_duration increase from it's previous value. For example, I can change the value to "1" during an iteration, and instead of changing to "2" during the next iteration, it will be the value of "t". I've simplified the code a good amount below so please let me know if what I am asking is not clear. Any help is appreciated!

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Santhana Raj 2017-5-31

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does this work for you?

    for t=1:24
        hour = t;
      if any( any( ~X(xpos+1:xpos+10, ypos+1:ypos+10) ) )
           trip_duration=0;
      else
           trip_duration=t;
      end
  end