How to avoid a for loop in functions?

Question

Prasanna 2020-2-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/506272-how-to-avoid-a-for-loop-in-functions

评论： Star Strider 2020-2-19

Hi All,

I have the following for loop in my matlab code and I was wandering is there any effcient way to implement this than using a for loop and going through each element.

press = 0:5/1000:5;
PsolWB = [];
for i = 1:length(press)
    
    if (press(i)<=1.6)
        PsolWB(i) = (973.-(70400./(1000.*press(i)+354.))+(77800000./(1000.*press(i)+354.).^2.)-273.15);
    else 
        PsolWB(i)=(935.+3.5.*press(i)+6.2.*press(i).^2-273.15);
  
    end
end

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Answer 1

Star Strider 2020-2-18

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/506272-how-to-avoid-a-for-loop-in-functions#answer_416238

在 MATLAB Online 中打开

Use ‘logical indexing’ and anonymous functions to eliminate the for loop and the if block:

PsolWB1 = @(press) (973.-(70400./(1000.*press+354.))+(77800000./(1000.*press+354.).^2.)-273.15);
PsolWB2 = @(press) (935.+3.5.*press+6.2.*press.^2-273.15);
PsolWB = @(press) PsolWB1(press).*(press <= 1.6) + PsolWB2(press).*(press > 1.6);
press = 0:5/1000:5;
figure
plot(press, PsolWB(press))
grid