fscanf problem with reading txt data.

fid = fopen('current.txt')  %Open source file "current.txt"
NumSV = fscanf(fid, '%d')    %Number of Satellites (PRN)
name = fgetl(fid)
[data, count] = fscanf(fid,'%f')
fclose(fid)

%I need to extract related information from current.txt file with using fscanf but it creates empty matrix like,

NumSV =

     []

[per isakson]

• "with using fscanf" &nbsp Why fscan?
• What exactly do you want to read from the file?

[sermet]

I need to determine how many PRN exist in current.txt

Answer 1

[Star Strider]

I would use textscan.

This works:

fidi = fopen('current.txt', 'rt');
NumSV = textscan(fidi, '%s%f', 'HeaderLines',1, 'EndOfLine','\r\n', 'Whitespace',' ', 'Delimiter',':');

strings = NumSV{1};
numeric = NumSV{2};

It reads in the entire file. The individual satellites are separated by NaN values in the ‘numeric’ vector, corresponding to the ‘******** Week 806 ...’ lines.

EDIT — To count the number of satellites, count the number of NaN values in the ‘numeric’ vector:

NumberOfSatellites = size(isnan(numeric), 1);

When I ran my code with your file, the result was:

NumberOfSatellites =

      20

[srt10]

The attached text file by OP actually lists 32 satellites. You only got 20 with your code. Not sure why you're telling him to use textscan instead of fscanf when the code you gave him doesn't work.

This also doesn't address the question of why fscanf would fail in the first place. I have the same problem where fscanf returns an empty array.

fileid = fopen("spectrum.txt",'r');
spectra=fscanf(fileid,'%f',[2 Inf]);

I can get it work only if I add a fgetl command in the middle.

fileid = fopen("spectrum.txt",'r');
tline = fgetl(fileid);
spectra=fscanf(fileid,'%f',[2 Inf]);

This makes no sense. I have attached the file if you want to check for yourself.

[Stephen23]

"This also doesn't address the question of why fscanf would fail in the first place"

It fails for exactly the same reason that your first attempt does not work.

"This makes no sense. I have attached the file if you want to check for yourself."

I checked your file. This is what the first few lines look like:

Wavelength	Intensity
1.000000000000E+3	1.400000000000E+0
1.000058651026E+3	1.350000000000E+0
1.000117302053E+3	2.300000000000E+0
1.000175953079E+3	3.100000000000E+0
1.000234604106E+3	2.800000000000E+0
... etc

Your first attempt to import the file used fscanf with '%f' format string. The fscanf documentation states that "If fscanf cannot match formatSpec to the data, it reads only the portion that matches and stops processing".

Question: what is the very first character of the file?

Answer: 'W'

Question: does 'W' match the numeric format string specified (i.e. is it recognised as being part of a number)?

Answer. no.

Question: what does the documentation say happens if the data does not match the specified format?

Answer: it stops processing (thus the empty output).

With your second attempt you read (and discard) the first line (which contains non-number characters). The rest of the file contains only numbers and whitespace, which are read exactly as documented by the '%f' format specified.

So far everything works exactly as documented and expected.

[srt10]

Thanks for your reply. I understand now.