How to read text fields into MATLAB and create a single matrix

Question

I have a huge CSV file that has a mix of numerical and text datatypes. I want to read this into a single matrix in Matlab. I'll use a simpler example here to illustrate my problem. Let's say I have this CSV file:

1,foo
2,bar

I am trying to read this into MatLab using:

A=fopen('filename.csv');
B=textscan(A,'%d %d', 'delimiter',',');
C=cell2mat(B);

The first two lines work fine, but the problem is that texscan doesn't create a 2x2 matrix; instead it creates a 1x2 matrix with each value being an array. So I try to use the last line to combine the arrays into one big matrix, but it generates an error because the arrays have different datatypes.

Is there a way to get around this problem? Or a better way to combine the arrays?

Answer 1

I believe you can't use textscan for this purpose. I'd use fscanf which always gives you a matrix as specified. If you don't know the layout of the data it gets kind of tricky however.

fscanf works as follows:

fscanf(fid, format, size)

where fid is the fid generated by the fopen

format is the file format & how you are reading the data (['%d' ',' '%s'] would work for your example file)

size is the matrix dimensions ([2 2] would work on your example file).

Answer 2

I am note sure if combining them is a good idea. It is likely that you would be better off with them separate.

I changed your code, so that it works better:

clear
clc
A=fopen('filename.csv');
B=textscan(A,'%d %s', 'delimiter',',')
fclose(A)

Looking at the results

K>> B{1}

ans =

       1
       2

K>> B{2}

ans =

'foo'
'bar'

Really, I think this is the format that is most useful. If anything, most people would want to break this cell array into smaller chunks

num = B{1}
txt = B{2}

Why are your trying to combine them? They are already together in a cell array, and that is the most combined you are going to get.

Answer 3

There is a natural solution to this, but it requires the Statistics toolbox (version 6.0 or higher). Mixed data types can be read into a dataset array. See the Mathworks help page here.

Answer 4

Look on MatlabCC for a file called "readtext", works wonders...