MATLAB: Simple for loop efficiency

for loopMATLABspeed

Hello, this is my first post here. Currently I am working on a script that should recalculate the column numbers as following:
firstvalue = table{1,1};
i = 1;
height = height(table);
for i = 1:height
    x = table{i,1};
    table{i,1} = (x-firstvalue)/fs*1000;
    i = i+1;
end
This loop does what I want, but is terribly slow. Is there a way to make this loop execute faster? The loop works in the table with around 50.000 rows. I think the loop could be more efficient but don't know how.
Thank you!

Best Answer

How about doing this.
table{:,1} = (table{:,1}-table{1,1})/fs*1000;
And let's check the calculation time.
 fs = 100;
 table1 = array2table(rand(1000,2));
 table2 = table1;
 % Slightly modified original code
 tic
 firstvalue = table1{1,1};
 i = 1;
 n = height(table1);
 for i = 1:n
    x = table1{i,1};
    table1{i,1} = (x-firstvalue)/fs*1000;
 end
 toc
 % Proposed code
 tic
 table2{:,1} = (table2{:,1}-table2{1,1})/fs*1000;
 toc
 % Check the answer
 isequal(table1, table2)
In my PC, the result is 0.131066 sec -> 0.003073 sec and table2 is the same as table1.
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