Fortran to Matlab converting the "where" statement

Question

msh 2014-6-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/133589-fortran-to-matlab-converting-the-where-statement

编辑： James Tursa 2014-6-11

采纳的回答： James Tursa

在 MATLAB Online 中打开

Hi,

I would like to know how is possible to convert the particular statement from fortran to matlab

where (abs(A-B)>e)
    no_converge=1
elsewhere
    no_converge=0
end where

A and B are arrays of some particular dimensions, and e is a scalar. I have to say that I am not that familiar with either programming languages. However, what I understood from some sources the particular statement takes the element per element difference of those arrays and evaluates whether the difference is higher or lower from a particular scalar, e. For this example, assume that it is very small, e.g e=0.0001.

I have used the f2matlab but it does very poor job on this fortran statement. In case it helps this is a code from F90.

I am wondering whether the quivalent for a matlab is something like this:

if abs(A-B)>e
    no_converge=1 ;
else 
    no_converge=0 ; 
end

However, I am not sure whether this is quite general or not. In other words, i am not sure for whatever the condition is or the A's and B's a simple "if" statement does the trick.

I will really appreciate any suggestions here. In case that it helps, this part of the code, is very crucial since it checks whether a whole distribution converges to a particular distribution that is needed.

Many thanks

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Answer 1

James Tursa 2014-6-10

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/133589-fortran-to-matlab-converting-the-where-statement#answer_140303

编辑：James Tursa 2014-6-11

在 MATLAB Online 中打开

no_converge= zeros(size(A));
no_converge( abs(A-B) > e ) = 1;

or

no_converge= double( abs(A-B) > e );

or if you can use no_converge as a logical instead of a double:

no_converge= abs(A-B) > e;

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James Tursa 2014-6-11

编辑：James Tursa 2014-6-11

@Safis: What you have written makes absolutely no sense to me at all. The WHERE construct is specifically set up to do element-by-element assignments to arrays controlled by the logical array mask. The variable being assigned to, no_converge, only makes sense in this context if it is an array. Can you double check your code? In addition to the INTEGER statement, is no_converge also part of a separate DIMENSION statement?

msh 2014-6-11

@James Tursa: You are right, the authors of the code indeed have declared the no_converge as an array of the same dimensions as in A and B. I got confused because they also have another no_converge_f variable declared as an integer. I now i believe I got it. Thanks

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