Reading specific data from a txt/csv 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!

Answer 1

[Matt Tearle]

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.

[Hissam Aziz]

Thank you so much for your help! At the moment i'm not sure how all of this works, and i'm not sure why its not working at the moment. I think i'll spend some time de-coding your text and understand it in detail! I love the fact that you converted the mintues and seconds to decimal! That makes my job so much easier!

[Hissam Aziz]

i have another question related to this, maybe you can help. I'm trying to store this number 46.000083201, do you know what format i should store it in? matlab keeps rounding it up to 46.0001. I've tried all possible combinations, %f64 %d32 etc.

[Debjit Pal]

Possibly before you store you can execute

>> format long

That will do the job I guess

[Matt Tearle]

There's an important distinction between how MATLAB stores numbers and how they are displayed. But default, numbers are stored as double precision in MATLAB (about 16 decimals) but displayed to the Command Window to 4 d.p. If you use %f in textscan, you'll get doubles. If you want to see more decimals in the display, you can use the format command to set the default display format, as Debjit Pal suggests, or use something like fprintf to print values out to a fixed format.

Answer 2

[Seyedali Pourmoafi]

Hi everyone,

I want to read so specific data from a CSV file and there are not numeric formats, there are some names. could you please help me in this regard? How can I do it?