speed optimization in "for" loops
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Hi,
I have an experiment with 864 trials. I have an array named Edf_Trials3, with data of saccadic eye movements during the entire experiment. In some trials I have more than one eye movement, in others there is none.
I have an other array, named Time_EndPpt6, with the time of the stimuli presentation in each trial.
I would like to add the time of the stimuli presentation in the former array "Edf_Trials3", on the same line of the corresponding trial.
For that i'm using 2 loops but it's very very long.
Could you help to simplify my code in order to boost the process ?
I add the two arrays. this is my code:
for (j=1:height(Edf_Trials3))
for(i=1:length(Time_EndPpt6))
if (Edf_Trials3.Trial(j)==i)
Edf_Trials3.EndTime_of_Ppt(j)=Time_EndPpt6(i);
end
end
end
Thanks for your help
1 个评论
Jan
2018-10-24
I'd omit the strange parentheses for the for and if commands. It works, but does not look Matlabish.
采纳的回答
The code overwrites Edf_Trials3.EndTime_of_Ppt(j) repeatedly. Then you can run the inner loop in backward direction and stop at the first match:
% [EDITED] pre-allocation
Edf_Trials3.EndTime_of_Ppt = zeros(1, height(Edf_Trials3));
for j = 1:height(Edf_Trials3)
for i = length(Time_EndPpt6):-1:1
if Edf_Trials3.Trial(j) == i
Edf_Trials3.EndTime_of_Ppt(j) = Time_EndPpt6(i);
break; % Stop "for i" loop early
end
end
end
You could try a vectorization also:
% [EDITED] pre-allocation, typo: "m" -> "idx"
tmp = zeros(1, height(Edf_Trials3));
v = 1:length(Time_EndPpt6);
for j = 1:height(Edf_Trials3)
idx = find(Edf_Trials3.Trial(j) == v, 1, 'last');
tmp(j) = Time_EndPpt6(idx);
end
Edf_Trials3.EndTime_of_Ppt = tmp;
How large are the inputs? Can you post some relevant small example data?
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