speed up for and if loop

Question

Frederik Reese 2022-8-3

0
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https://ww2.mathworks.cn/matlabcentral/answers/1773170-speed-up-for-and-if-loop

评论： Frederik Reese 2022-8-3

在 MATLAB Online 中打开

Hi,

I want to get better in programming.

my Code works well but how can I speed up the calculation?

Thanks in andvance

for y=1:size(Wasserhoehe_HQ10000,1)%4585
    for i= 1:10000% 2: size(FRI_10000_EventPhase,2);% 155 
        if isnan(Zeit_Flutende_10000_BA(y,:))==1
            FRI_RecoveryPhase_10000(y,:)=nan;
        else
        if i == 1  % für ersten FRI Recovery letzten FRI Event als start
            FRI_RecoveryPhase_10000(y,1)=FRI_10000_EventPhase(y,Zeit_Flutende_10000_BA(y,:)-1 ).*RF_10000(y,:);
        else
     FRI_RecoveryPhase_10000(y,[i])=FRI_RecoveryPhase_10000(y,i-1).*RF_10000(y,:); %4585X155
        end
        end
    end
end 

4 个评论
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Jan 2022-8-3

There are no "if loop" in any programming language I know.

Do not store data in the name of variables. "Wasserhoehe_HQ10000" is too long to be readable. All variables contain a "10000", so this is redundant and should be omitted.

"rows which are nan" - this is still not clear: do you mean, that all elements of this row are NaN's or if any element is NaN?

Bruno Luong 2022-8-3

"...that all elements of this row are NaN's or if any element is NaN?"

it's the same since

"Zeit_Flutende_10000_BA has only one column."

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Answer 1

Jan 2022-8-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1773170-speed-up-for-and-if-loop#answer_1020400

在 MATLAB Online 中打开

isnan replies trtue or false. There is no need to compare it with ==1 afterwards.

nWasserhoehe = size(Wasserhoehe_HQ, 1);
FRI_RecoveryPhase = zeros(nWasserhoehe, 10000);   % Pre-allocation!!!
for y = 1:nWasserhoehe  % 4585
    RFy = RF(y, :);  % Temporary variable
    % für ersten FRI Recovery letzten FRI Event als start
    FRI_RecoveryPhase(y, 1) = FRI_EventPhase(y, Zeit_Flutende_BA(y, :) - 1) .* RFy;    
    for i = 2:10000     % 2: size(FRI_EventPhase,2);% 155 
        if isnan(Zeit_Flutende_BA(y, :))  % any() or all() ?!?
            FRI_RecoveryPhase(y, :) = nan;
        else
            FRI_RecoveryPhase(y, i) = FRI_RecoveryPhase(y, i - 1) .* RFy;  %4585X155
        end
    end
end 