VERY slow for loop

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sani
sani 2020-1-18
编辑： sani 2020-1-19
I have a very slow for loop in my script, it meant to sort a column in a text file (about 500,000 rows) and remove lines with negative values. it took ~10600 sec to finish this lines. Is this normal? any way to improve it?
this is the code:
for i = 1:height (T1(:,2)) %remove negative numbers from column 2
if lt(T1.energy,0)
continue;
else
T1(T1.energy < 0, :) = [];
end
end
thanks!

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采纳的回答

Walter Roberson
Walter Roberson 2020-1-18
You do not use the variable i inside your for loop, so you are testing the entire energy variable of the table every time through the loop.
if lt(T1.energy,0)
is a vector test, and will only be true if all of the entries in T1.energy are < 0 .
You probably just want,
T1(T1.energy < 0, :) = [];
with no loop -- just the single statement.

更多回答（1 个）

sani
sani 2020-1-19
编辑：sani 2020-1-19
thanks! it reduced to 0.3 sec, amazing!

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