I am using the following functions for writing and reading 4098 floating point numbers in MATLAB:
Writing:
fid = fopen(completepath, 'w');
fprintf(fid, '%1.30f\r\n', y)
Reading:
data = textread(completepath, '%f', 4098);
where y contains 4098 numbers. I now want to write and read 3 strings at the end of this data. How do I read two different datatypes? Please help me. Thanks in advance.
Here's an example of what I think you want to do, using TEXTSCAN for reading the file instead of TEXTREAD (which will be removed in a future version of MATLAB):
%# Writing to the file:
fid = fopen(completepath,'w'); %# Open the file
fprintf(fid,'%1.30f\r\n',y); %# Write the data
fprintf(fid,'Hello\r\n'); %# Write string 1
fprintf(fid,'there\r\n'); %# Write string 2
fprintf(fid,'world!\r\n'); %# Write string 3
fclose(fid); %# Close the file
%# Reading from the file:
fid = fopen(completepath,'r'); %# Open the file
data = textscan(fid,'%f',4098); %# Read the data
stringData = textscan(fid,'%s',3); %# Read the strings
fclose(fid); %# Close the file
Well, you can write out a string at any point when you are writing to the file with the following:
fprintf(fid, '%s', mystring);
Of course, you might want something more like the form you gave:
fprintf(fid,'%s\r\n', mystring);
And you could mix the floating point with the string like so:
fprintf(fid, '%1.30f %s\r\n', y, mystring);
If you are dealing with mixed data types, you might want to use fscanf instead of textread if the formatting isn't very regular. For instance,
data = fscanf(fid, '%s', 1);
reads one character string from the file.
Take a look at the help files for fscanf for more information on how to use it. These functions are pretty much ANSI C functions (fprintf and fscanf I mean) so you find more info on the web about them quite easily.
Related
What I have
A txt file like:
D091B
E7E1F
20823
...
What I need
To read them and store them like char, just as they are in the file: N (don't knot how many) lines, with its 5 characters (5 columns) at each one.
What have I tried
fichero = fopen('PS.txt','r');
sizeDatos = [[] 5]; % Several Options, read below
resultados=fscanf(fichero, '%s', sizeDatos); % Here too
fclose(fichero);
I've tried with the snippet above, to read my txt file. However, I didn't manage to get it. Most I've obtained is, using:
sizeDatos = [1 Inf];
So I got all my hex characters into an array, with no spaces.
As you can see, I've tried several optios changing fscanf size parameter, as well as trying to say into the format chain that it should recognize new lines by using \n for example. None of them have worked for me.
Any idea about how can I get it? I've readed fscanf page from documentation, but it didn't inspire me to make anything different.
One possible solution is using textscan and convert it to a cell array.
fileId = fopen('PS.txt');
C = textscan(fileId, '%s');
Now to show the content of cell you can use
celldisp(C)
Or you can convert it to other types.
Don't forget to close your file after using it.
I have a very large matrix (M X N). I want to divide matrix into 10 equal parts (almost) and save each of them into a separate file say A1.txt, A2.txt, etc. or .mat format. How can I do this ?
Below is a code to divide a matrix into 10 equal parts and data_size is (M / 10).
for i=1:10
if i==1
data = DATA(1:data_size,:);
elseif i==10
data = DATA((i-1)*data_size+1:end,:);
else
data = DATA((i-1)*data_size+1: i*data_size,:);
end
save data(i).mat data
% What should I write here in order to save data into separate file data1.mat, data2.mat etc.
end
You said you wanted it in either txt format or mat format. I'll provide both solutions, and some of this is attributed to Daniel in his comment in your post above.
Saving as a text file
You can use fopen to open a file up for writing. This returns an ID to the file that you want to write to. After this, use fprintf and specify the ID to the file that you want to write to, and the data you want to write to this file. As such, with sprintf, generate the text file name you want, then use fprintf to write data to your file. It should be noted that writing matrices to fprintf in MATLAB assume column major format. If you don't want your data written this way and want it done in row-major, you need to transpose your data before you write this to file. I'll provide both methods in the code depending on what you want.
After you're done, use fclose to close the file noting that you have finished writing to it. Therefore, you would do this:
for i=1:10
if i==1
data = DATA(1:data_size,:);
elseif i==10
data = DATA((i-1)*data_size+1:end,:);
else
data = DATA((i-1)*data_size+1: i*data_size,:);
end
filename = sprintf('A%d.txt', i); %// Generate file name
fid = fopen(filename, 'w'); % // Open file for writing
fwrite(fid, '%f ', data.'); %// Write to file - Transpose for row major!
%// fwrite(fid, '%f ', data); %// Write to file - Column major!
fclose(fid); %// Close file
end
Take note that I space separated the numbers so you can open up the file and see how these values are written accordingly. I've also used the default precision and formatting by just using %f. You can play around with this by looking at the fprintf documentation and customizing the precision and leading zero formatting to your desire.
Saving to a MAT file
This is actually a more simpler approach. You would still use sprintf to save your data, then use the save command to save your workspace variables to file. Therefore, your loop would be this:
for i=1:10
if i==1
data = DATA(1:data_size,:);
elseif i==10
data = DATA((i-1)*data_size+1:end,:);
else
data = DATA((i-1)*data_size+1: i*data_size,:);
end
filename = sprintf('A%d.mat', i); %// Generate file name
save(filename, 'data');
end
Take note that the variable you want to save must be a string. This is why you have to put single quotes around the data variable as this is the variable you are writing to file.
You can use
save(['data' num2str(i) '.mat'], 'data');
where [ ] is used to concatenate strings and num2str to convert an integer to a string.
I have a .tsv file that I wish to open in MATLAB, however I am having several problems with this.
I have tried the following
fid = fopen('data.tsv');
C = textscan(fid, ['%s' repmat('%f',1,8)], 'HeaderLines', 1);
fclose(fid);
and got some weird values that had nothing to do with my file. I also tried:
data = dlmread('data.tsv', '\t');
and got this
Error using dlmread (line 139)
Mismatch between file and format string.
Trouble reading number from file (row 1u, field 1u) ==> Participant Assessment
Experiment Block Trial
Answer Reaction Timestamp Free Response\n
Is there some way I can get it to ignore the header, or am I doing it totally wrong?
With dlmread you can specify where to start reading in the file. This is one of the few times that MATLAB indexing begins at 0 - [0,0] is the first row, first column. Therefore, to ignore the first row (containing your header):
data = dlmread('data.tsv','\t', 1, 0);
This will only work if all the values (other than the header lines you skip) are numeric.
Your example with textscan also looks fine to me (provided that the format supplied is correct and there is indeed only one header line). C will be a cell array; to obtain the data from each column use C{n} where n is the column number.
Rather than skipping the header line, it's sometimes useful to just read it in to a separate value:
fid = fopen('data.tsv');
C_header = textscan(fid, '%s',9);
C = textscan(fid, ['%s' repmat('%f',1,8)]);
fclose(fid);
I have a big text file containing data that needs to be extracted and inserted into a new text file. I possibly need to store this data in an cell/matrix array ?
But for now, the question is that I am trying to test a smaller dataset, to check if the code below works.
I have a code in which it opens a text file, scans through it and replicates the data and saves it in another text file called, "output.txt".
Problem : It doesn't seem to save the file properly. It just shows an empty array in the text file, such as this " [] ". The original text file just contains string of characters.
%opens the text file and checks it line by line.
fid1 = fopen('sample.txt');
tline = fgetl(fid1);
while ischar(tline)
disp(tline);
tline = fgetl(fid1);
end
fclose(fid1);
% save the sample.txt file to a new text fie
fid = fopen('output.txt', 'w');
fprintf(fid, '%s %s\n', fid1);
fclose(fid);
% view the contents of the file
type exp.txt
Where do i go from here ?
It's not a good practice to read an input file by loading all of its contents to memory at once. This way the file size you're able to read is limited by the amount of memory on the machine (or by the amount of memory the OS is willing to allocate to a single process).
Instead, use fopen and its related function in order to read the file line-by-line or char-by- char.
For example,
fid1 = fopen('sample.txt', 'r');
fid = fopen('output.txt', 'w');
tline = fgetl(fid1);
while ischar(tline)
fprintf(fid, '%s\n', tline);
tline = fgetl(fid1);
end
fclose(fid1);
fclose(fid);
type output.txt
Of course, if you know in advance that the input file is never going to be large, you can read it all at once using by textread or some equivalent function.
Try using textread, it reads data from a text file and stores it as a matrix or a Cell array. At the end of the day, I assume you would want the data to be stored in a variable to manipulate it as required. Once you are done manipulating, open a file using fopen and use fprintf to write data in the format you want.
I have a text file which has 4 columns, each column having 65536 data points. Every element in the row is separated by a comma. For example:
X,Y,Z,AU
4010.0,3210.0,-440.0,0.0
4010.0,3210.0,-420.0,0.0
etc.
So, I have 65536 rows, each row having 4 data values as shown above. I want to convert it into a matrix. I tried importing data from the text file to an excel file, because that way its easy to create a matrix, but I lost more than half the data.
If all the entries in your file are numeric, you can simply use a = load('file.txt'). It should create a 65536x4 matrix a. It is even easier than csvread
Have you ever tried using 'importdata'?
The parameters you need only file name and delimiter.
>> tmp_data = importdata('your_file.txt',',')
tmp_data =
data: [2x4 double]
textdata: {'X' 'Y' 'Z' 'AU'}
colheaders: {'X' 'Y' 'Z' 'AU'}
>> tmp_data.data
ans =
4010 3210 -440 0
4010 3210 -420 0
>> tmp_data.textdata
ans =
'X' 'Y' 'Z' 'AU'
Instead of messing with Excel, you should be able to read the text file directly into MATLAB (using the functions FOPEN, FGETL, FSCANF, and FCLOSE):
fid = fopen('file.dat','rt'); %# Open the data file
headerChars = fgetl(fid); %# Read the first line of characters
data = fscanf(fid,'%f,%f,%f,%f',[4 inf]).'; %'# Read the data into a
%# 65536-by-4 matrix
fclose(fid); %# Close the data file
The easiest way to do it would be to use MATLAB's csvread function.
There is also this tool which reads CSV files.
You could do it yourself without too much difficulty either: Just loop over each line in the file and split it on commas and put it in your array.
Suggest you familiarize yourself with dlmread and textscan.
dlmread is like csvread but because it can handle any delimiter (tab, space, etc), I tend to use it rather than csvread.
textscan is the real workhorse: lots of options, + it works on open files and is a little more robust to handling "bad" input (e.g. non-numeric data in the file). It can be used like fscanf in gnovice's suggestion, but I think it is faster (don't quote me on that though).