Reading CSV with mixed type data - matlab

Question

I need to read the following csv file in MATLAB:
2009-04-29 01:01:42.000;16271.1;16271.1
2009-04-29 02:01:42.000;2.5;16273.6
2009-04-29 03:01:42.000;2.599609;16276.2
2009-04-29 04:01:42.000;2.5;16278.7
...
I'd like to have three columns:
timestamp;value1;value2
I tried the approaches described here:
Reading date and time from CSV file in MATLAB
modified as:
filename = 'prova.csv';
fid = fopen(filename, 'rt');
a = textscan(fid, '%s %f %f', ...
'Delimiter',';', 'CollectOutput',1);
fclose(fid);
But it returs a 1x2 cell, whose first element is a{1}='ÿþ2', the other are empty.
I had also tried to adapt to my case the answers to these questions:
importing data with time in MATLAB
Read data files with specific format in matlab and convert date to matal serial time
but I didn't succeed.
How can I import that csv file?
EDIT After the answer of #macduff i try to copy-paste in a new file the data reported above and use:
a = textscan(fid, '%s %f %f','Delimiter',';');
and it works.
Unfortunately that didn't solve the problem because I have to process csv files generated automatically, which seems to be the cause of the strange MATLAB behavior.

Answer 1

What about trying:
a = textscan(fid, '%s %f %f','Delimiter',';');
For me I get:
a =
{4x1 cell} [4x1 double] [4x1 double]
So each element of a corresponds to a column in your csv file. Is this what you need?
Thanks!

Answer 2

Seems you're going about it the right way. The example you provide poses no problems here, I get the output you desire. What's in the 1x2 cell?
If I were you I'd try again with a smaller subset of the file, say 10 lines, and see if the output changes. If yes, then try 100 lines, etc., until you find where the 4x1 cell + 4x2 array breaks down into the 1x2 cell. It might be that there's an empty line or a single empty field or whatever, which forces textscan to collect data in an additional level of cells.
Note that 'CollectOutput',1 will collect the last two columns into a single array, so you'll end up with 1 cell array of 4x1 containing strings, and 1 array of 4x2 containing doubles. Is that indeed what you want? Otherwise, see #macduff's post.

Answer 3

I've had to parse large files like this, and I found I didn't like textscan for this job. I just use a basic while loop to parse the file, and I use datevec to extract the timestamp components into a 6-element time vector.
%% Optional: initialize for speed if you have large files
n = 1000 %% <# of rows in file - if known>
timestamp = zeros(n,6);
value1 = zeros(n,1);
value2 = zeros(n,1);
fid = fopen(fname, 'rt');
if fid < 0
error('Error opening file %s\n', fname); % exit point
end
cntr = 0
while true
tline = fgetl(fid); %% get one line
if ~ischar(tline), break; end; % break out of loop at end of file
cntr = cntr + 1;
splitLine = strsplit(tline, ';'); %% split the line on ; delimiters
timestamp(cntr,:) = datevec(splitLine{1}, 'yyyy-mm-dd HH:MM:SS.FFF'); %% using datevec to parse time gives you a standard timestamp vector
value1(cntr) = splitLine{2};
value2(cntr) = splitLine{3};
end
%% Concatenate at the end if you like
result = [timestamp value1 value2];