read complicated .txt file into Matlab - string

Question

I would like to read a .txt file into Matlab.
One of the columns contains both letters and numbers.
(So I guess one way is to read this column is as string.)
The problem is I also need to find out numbers which are larger than 5 within that column.
e.g. The .txt looks like
12 1
21 2
32 7
11 a
03 b
22 4
13 5
31 6
i.e. Ultimately, I would like to get
32 7
31 6
How can I get it?? Any experts, please help!

Answer 1

You can read the contents of the file into a cell array of strings using TEXTSCAN, convert the strings to numeric values using CELLFUN and STR2NUM (characters like 'a' and 'b' will result in the empty matrix []), remove rows of the cell array that have any empty cells in them, then convert the remaining data into an N-by-2 matrix using CELL2MAT:
fid = fopen('junk.txt','r'); %# Open the file
data = textscan(fid,'%s %s','CollectOutput',true); %# Read the data as strings
fclose(fid); %# Close the file
data = cellfun(#str2num,data{1},'UniformOutput',false); %# Convert to numbers
data(any(cellfun('isempty',data),2),:) = []; %# Remove empty cells
data = cell2mat(data); %# Convert to N-by-2 array
The matrix data will now look like this, given your sample file in the question:
>> data
data =
12 1
21 2
32 7
22 4
13 5
31 6
And you can get the rows that have a value greater than 5 in the second column like so:
>> data(data(:,2) > 5,:)
ans =
32 7
31 6

Answer 2

fid = fopen('txt.txt','r');
Aout = [];
while(1)
[a1,count1] = fscanf(fid,'%s',1);
[a2,count2] = fscanf(fid,'%s',1);
if(count1 < 1 | count2 < 1)
break;
end
if(~isempty(str2num(a2)) & str2num(a2) > 5 & (~isempty(str2num(a1))) )
Aout = [ Aout ; str2num(a1) str2num(a2) ];
end
end
fclose(fid);
Violates the unspoken rule of growing a Matlab variable during a loop, but it's text processing anyway so you probably won't notice the slowness.
Edit: Had too many errors in previous version, had to start fresh.