Matlab String Conversion to Array

Question

I got a string array of the format

sLine = 
{
   [1,1] = 13-Jul-16,10.46,100.63,15.7,54.4,55656465
   [1,2] = 12-Jul-16,10.47,100.64,15.7,54.4,55656465
   [1,3] = 11-Jul-16,10.48,100.65,15.7,54.4,55656465
   [1,4] = 10-Jul-16,10.49,100.66,15.7,54.4,55656465
}

In which each element is a string ("13-Jul-16,10.46,100.63,15.7,54.4,55656465" is a string).

I need to convert this to 6 vectors, something like

[a b c d e f] = ...

such a way, for example, for the 1st column, it would be

a = [13-Jul-16;12-Jul-16;11-Jul-16;10-Jul-16]

I tried to use cell2mat function, but for some reason it does not separate the fields into matrix elements, but it concatenates the whole string into something like

cell2mat(sLine)
ans = 
     13-Jul-16,10.46,100.63,15.7,54.4,5565646512-Jul-16,10.47,100.64,15.7,54.4,5565646511-Jul-16,10.48,100.65,15.7,54.4,5565646510-Jul-16,10.49,100.66,15.7,54.4,55656465

So, how can I solve this?

Update

I got the sLine matrix following the steps

pFile = urlread('http://www.google.com/finance/historical?q=BVMF:PETR4&num=365&output=csv');
sLine = strsplit(pFile,'\n');
sLine(:,1)=[];

Update

Thanks to @Suever I could get now the column dates. So the updated last version of the code is

pFile = urlread('http://www.google.com/finance/historical?q=BVMF:PETR4&num=365&output=csv');
pFile=strtrim(pFile);
sLine = strsplit(pFile,'\n');
sLine(:,1)=[];

split_values = regexp(sLine, ',', 'split');

values =  cat(1, split_values{:});
values(:,1)

you cannot use cell2mat because a mat (numerical matrix) cannot contain strings. so you will need to use cell Arrays. The function you are looking for is strsplit — GameOfThrows
– GameOfThrows, Commented Jul 15, 2016 at 14:10
I tried strsplit before, but no success. Anyway I need to convert that string into numeric values, to put each numeric column in a separate vector. — Pablo Rego
– Pablo Rego, Commented Jul 15, 2016 at 15:50

Suever · Accepted Answer · 2016-07-15 15:24:46Z

2

Your data is all strings, therefore you will need to do some string manipulation rather than using cell2mat.

You will want to split each element at the ,characters and then concatenate the result together.

sLine = {'13-Jul-16,10.46,100.63,15.7,54.4,55656465',
         '12-Jul-16,10.47,100.64,15.7,54.4,55656465',
         '11-Jul-16,10.48,100.65,15.7,54.4,55656465',
         '10-Jul-16,10.49,100.66,15.7,54.4,55656465'};

split_values = cellfun(@(x)strsplit(x, ','), sLine, 'uniformoutput', 0);
values = cat(1, split_values{:});

values(:,1)

%   {
%     [1,1] = 13-Jul-16
%     [2,1] = 12-Jul-16
%     [3,1] = 11-Jul-16
%     [4,1] = 10-Jul-16
%   }

If you want it to be more concise, we can just use regexp to split it up instead of strsplit since it can accept a cell array as input.

split_values = regexp(sLine, ',', 'split');
values =  cat(1, split_values{:});

Update

The issue with the code that you've posted is that there is a trailing newline in the input and when you split on newlines the last element of your sLine cell array is empty causing your issues. You'll want to use strtrim on pFile before creating the cell array to remove trailing newlines.

sLine = strsplit(strtrim(pFile), '\n');
sLine(:,1) = [];

edited Jul 15, 2016 at 15:24

answered Jul 15, 2016 at 14:11

Suever

65.6k14 gold badges91 silver badges104 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Pablo Rego Over a year ago

Thank you for your quick answer. In my case there were a dimension mismatch in the cat call, and I realized that my sLine is a transposed of yours. But even transposing it does not fix the mismatch. I updated the post with the exact steps to get my sLine matrix, it should be a small detail I am not seeing. Thanks again.

Suever Over a year ago

@Rego Updated with a description of the reason you're having issues

Pablo Rego Over a year ago

Great, this way it has fixed the mismatch, so the column dates is correct. But I am trying to get the other columns using bO = cat(2, split_values{:}); and the result seems not be correct.

Suever Over a year ago

Why are you using the second dimension instead of the first?

Pablo Rego Over a year ago

bDates = cat(1, split_values{:}); get the first column, right? So I thought bO = cat(2, split_values{:}) gets the second column, bH = cat(3, split_values{:}) gets the third column, and so on?

|

Collectives™ on Stack Overflow

Matlab String Conversion to Array

1 Answer 1

8 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

8 Comments

Your Answer

Sign up or log in

Post as a guest

Related