MATLAB: An efficient way to import data containing letters and numbers

data importletters

Hello,

I am trying to generate some netcdf files with data sets containing numerical values along with data flags represented by numbers. Here is what some data looks like:

01108431895   487X   445X   599X   662X   726X 
01108431896   484X   535X   568X   702E   778X 
01108431897   465X   563X   666X   657X   701X 
01108431898   531E   514E   634E   614E   752E

Is there any way to import this data and use it to create 3-d arrays so it looks exactly the way it does above, with the letter flags?

Thanks, Dan

Best Answer

fid = fopen('YourFileName', 'rt');
indata = textscan(fid, '%s%s%s%s%s%s');
fclose(fid);

Now indata{1} will be a cell array of strings which is the first column, indata{2} will be a cell array of strings which is the second column, and so on.

If everything is in a netcdf file instead of a text file, the import methods would not be the same. I am not familiar enough with netcdf to advise.

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MATLAB: How to import a particular text file and plot.

By specifying a format string of '%s', you effectively asked textscan for a single output. But then you asked to read a string 5 times. Consequently output is a single cell which contains five things. Those five things are themselves cells, which contain the strings you want. (Confused?)

So to get the third header, do

header{1}{3}

Or, you could do

textscan(fid, '%s%s%s%s%s', 1, ...

In which case you will get back 5 cells. But then each of them contains a single cell (which contains a string)!

Unfortunately this is just the way textscan works. It makes sense for reading whole columns of data, but not so much for a header line.

You can always do what you were doing and add

header = header{1}

Or do it the other way I showed above and add

header = [header{:}]

Either way, then, header will be a 5-element cell array of the strings.

EDIT, attempting to clarify: textscan returns an n-element cell array, where n is the number of format specifiers in the format string. Each cell will contain the contents that were read from the file. If the contents were numeric, you'll just get a numeric array. But if they were strings, you'll get a cell array of strings. That's why you're ending up with cell arrays containing cell arrays.

MATLAB: Need help reading only the numeric data in a value that contains letters

Another approach:

fid = fopen('test.txt', 'r');
if fid == -1, error('Cannot open file'); end
S = fread(fid, [1, inf], '*char');
fclose(fid);
S(S > '9') = ' ';
D = reshape(sscanf(S, '%g'), [], 4);

Best Answer

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MATLAB: How to import a particular text file and plot.

MATLAB: Need help reading only the numeric data in a value that contains letters

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