Find Header in .CSV File and Read Column
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Jacee Johnson
on 24 May 2015
Commented: Star Strider
on 25 May 2015
I have a large number of .CSV files in one folder. These files have different columns of data. I need to locate the desired columns by matching the header(string) and read only these columns. Example:
Date Time Temp_F Temp_C Lights_ON A/C_ON
5/23/15 12:23:07 70 21 0 1
5/23/15 12:23:08 71 22 0 1
5/23/15 12:23:09 71 22 1 1
Date Time Temp_F Temp_C Temp_K Lights_ON A/C_ON
5/24/15 13:30:27 63 17 290 1 0
5/24/15 13:30:28 64 18 291 0 0
5/24/15 13:30:29 65 18 291 1 0
I'd like to read Time, Temp_C and Lights_ON from these two files.
Before, the data was the same in all the files. I knew which columns to read and which columns to skip and was using the following code:
c = textscan('%*s%s%*d%d%d%*d', 'Delimiter', ',', 'Headerlines', 1);
Now I need to sort through the headers and match the strings and only read those columns. How would I go about doing this? Can I use textscan to accomplish this? Or maybe csvread or another command? I have attached a sample .CSV file. Thanks in advance.
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Accepted Answer
Star Strider
on 24 May 2015
Edited: Star Strider
on 25 May 2015
This is one way to approach it:
[n,s,r] = xlsread('Jacee Johnson Book1.csv');
des_cols = {'Time', 'Temp_C', 'Lights_ON'};
colhdrs = s(1,:);
[~,ia] = intersect(colhdrs, des_cols);
colnrs = flipud(ia);
Data = n(:, colnrs-1);
It first reads the file in, then compares the column headers to your desired strings to find the desired columns in ‘colnrs’. Since ‘n’ here is a double array, it then selects the desired columns by numbers, and returns them in ‘Data’. The ‘n’ variable does not include the date (a string), so I subtracted 1 from those columns so they would match appropriately. The time (in Data(:,1) here) is in fractions of a day.
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More Answers (1)
Walter Roberson
on 24 May 2015
Consider using the relatively new readtable() as that allows you to address content by column name.
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