MATLAB: Reading specific data from a txt/csv file

.csv fileintegralplotread dataspecific columnstxt file

Hi Everyone, i'm relatively new to Matlab and this is my first post on Mathworks! Wohoo! Will be grateful for any help!
So i'm trying to read data generated from a device which measures the energy consumption. When the csv/text file is generated it looks like this:
03/27/2013 11:20:46.000000000 PM;0.46957; 0.00002
03/27/2013 11:20:46.000083201 PM;0.45180; 0.00000
03/27/2013 11:20:46.000166402 PM;0.45180; 0.00007
My aim is to read "11:20:46.000000000" as a time stamp (the hour can be removed, all the need are the minutes and seconds" and "0.46957" as the power consumed, continuously for each row. This data will eventually be plotted and after curve fitting an integral.
I'm not sure how to how to achieve this. How do i read the time, and the energy? How do i read the time so that it can be considered as data and plotted? The file is huge, around 300 Megabytes. I can read simple csv files sure, but this file is structured strange and generated from C++ and i'm not sure i can change anything within the code, nor am i allowed to make any changes :S so the csv file will stay as is. Any help would be greatly appreciated! Thank you!

Best Answer

If you have a recent version of MATLAB, you can use the Import Tool to do it interactively, then generate the code. Or you can jump straight to the joy of the textscan function!
Do you need the dates at all? It sounds like the only time information you want is minutes and seconds. So:
fid = fopen('filename.txt');
rawdata = textscan(fid,'%*s %*f %f %f %*s %f %*f','delimiter',{' ',';',':'},...
    'MultipleDelimsAsOne',true);
times = rawdata{1} + rawdata{2}/60;
powconsumed = rawdata{3};
fid = fclose(fid);
This treats the file as a string (the date) followed by a space delimiter, followed by three numbers separated by a : delimiter, followed by a space delimiter and another string ("PM"), then two numbers separated by a ; delimiter. The * characters in the format string tell textscan to ignore those fields, so it just reads the minute, second, and power fields. I'm also converting minutes and seconds to a decimal minute (minute + second/60). You can change that to whatever you want -- keep them separate if you want.
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