How to avoid a for loop in functions?

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

Answer 1

[Star Strider]

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

This takes advantage of MATLAB’s vectorisation capabilities.

The plot is simply to demonstrate the result. It is not necessary for the code.

[Prasanna]

Thanks Star Strider. That helped.

[Star Strider]

As always, my pleasure!