Thread Subject:

need to modify some values in a multidimensional array

I am using mvnrnd() to create random climate in a multidimensional array. However, some of the values are nonsensical (such as precipitation values less than zero. To correct this problem, I tried to use an if statement to identify and replace negative precipitation values with 0.

Here is the code which inserts the output of mvnrnd into the final 200 years of monthly climate rows, for columns 3 through 6, for all arrays i. Precipitation is in column 6.

for i = 1:n;

    climate(12001:14400,3:6,i) = mvnrnd(muPost,sigmaPost);
    
end;

if climate(:,6,:) < 0
    climate(:,6,:) = 0;
end

Obviously my if statement is not doing what I think it should. Any suggestions would be appreciated. Thanks in advance.

"Kirk" <kwythers.nospam@umn.edu> wrote in message <iukq42$o5b$1@newscl01ah.mathworks.com>...
> I am using mvnrnd() to create random climate in a multidimensional array. However, some of the values are nonsensical (such as precipitation values less than zero. To correct this problem, I tried to use an if statement to identify and replace negative precipitation values with 0.
>
> Here is the code which inserts the output of mvnrnd into the final 200 years of monthly climate rows, for columns 3 through 6, for all arrays i. Precipitation is in column 6.
>
> for i = 1:n;
>
> climate(12001:14400,3:6,i) = mvnrnd(muPost,sigmaPost);
>
> end;
>
> if climate(:,6,:) < 0
> climate(:,6,:) = 0;
> end
>
> Obviously my if statement is not doing what I think it should. Any suggestions would be appreciated. Thanks in advance.

Without an example of your input data I can't guarantee this will be applicable to your situation, but here is a simple example that accomplishes something similar using randomized data:
input = random('normal', 0, 1, 4,4);
input (:,:, 2) = random('normal', 0,2, 4,4);
idx = input(:,:,1) <0;
output = input(:,:,1);
output(idx) = 0;
input(:,:,1) = output;

Kirk wrote:

...


> use an if statement to identify and replace negative precipitation
> values with 0.
...


> if climate(:,6,:) < 0
> climate(:,6,:) = 0;
> end
...


climate(climate(:,6,:) == 0) = 0;

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