I have 20 text files each containing a vector of size 180. How can I access each text file and assign the vector to a variable?
If you want to do it manually use Import Data under File (or use uiimport).
If you want to automate it use fid = fopen(filename) and then use var = textscan(fid, 'format') where format depends on how your vectors are structured. Spend some time reading doc textscan and doc fopen everything you probably need to know is in those two files. If your data is nicely structured look at doc importdata.
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I have a sequence of data files(".tab" files) with more than 11100 rows and 236 columns. Data begins from 297th line in one file and from 299th line in another file. How can I read the data from 297th row of each file in MATLAB R2014a?
I am not quite sure, bu it seems that a typical machine's memory can handle such a file size. In that case, you can use textscan or textread MATLAB built-in functions.
Nonetheless, if you really cannot import your data into MATLAB environment, set HeaderLines argument of textscan to the line of interest. A simple example can be found in MATLAB documentations, or:
SelectedData = textscan(ID,formatSpec,'HeaderLines',296); % Ignore 296 first lines of the data
First of all, I strongly recommend to review the MATLAB documentation. Assuming you have several files in hand (stored in fileNames:
for i = 1:numel(fileNames)
ID = fopen(fileNames{i});
formatSpec = '%s %[^\n]'; % Modify this based on your file structure
SelectedData{i} = textscan(ID,formatSpec,'HeaderLines',296);
fclose(ID);
end
SelectedData is a cell string containing all your data extracted from corresponding data (fileNames)
I have a tab delimited text file with suffix .RAW.
How can I load the data from the file into a matrix in MATLAB?
I have found readtable, but it doesn't support files ending with suffix .RAW.
Do I really have to use fread, fscanf, etc. to simply load a text file into a matrix?
You can use the dlmread() function. It will read data from an ASCII text file into a matrix and let you define the delimiter yourself. The delimiter for tabs is '\t'.
>> M = dlmread('Data.raw', '\t')
M =
1 2 3
4 5 6
7 8 9
Just for your information there is also the tdfread() function but I do not recommend using it except in very specific cases. dlmread() is a much better option.
.RAW is a generic file extention. You should know the format of your RAW file (especially if your file contains a combination of numbers, data structures etc). If it is a simple text file with a single 2D table, you can easily read it with fscanf, fread, fgetl, fgets, etc
Here is a simple example for a 2D table (matrix):
Let's assume that each row of your table is separated by a carriage return from its following rows. We can read each row by fgetl() and then extract numbers using str2num().
fid=fopen('YourTextFile.RAW');
Data=[];
i = 0;
while 1
i = i + 1;
tline = fgetl(fid);
if ~ischar(tline), break, end
Data(i,:) = str2num(tline);
end
fclose(fid);
disp(Data)
For more complex data structure, the code should be changed.
For a 2D table (a special case) the above simple code can be easily exchanged by dlmread() function.
Ok, so I'm struggling with the most mundane of things I have a space delimited text file with a header in the first row and a row per observation and I'd like to open that file in matlab. If I do this in R I have no problem at all, it'll create the most basic matrix and voila!
But MATLAB seems to be annoying with this...
Example of the text file:
"picFile" "subjCode" "gender"
"train_1" 504 "m"
etc.
Can I get something like a matrix at all? I would then like to have MATLAB pull out some data by doing data(1,2) for example.
What would be the simplest way to do this?
It seems like having to write a loop using f-type functions is just a waste of time...
If you have a sufficiently new version of Matlab (R2013b+, I believe), you can use readtable, which is very much like how R does it:
T = readtable('data.txt','Delimiter',' ')
There are many functions for manipulating tables and converting back and forth between them and other data types such as cell arrays.
There are some other options in the data import and export section of the Statistics toolbox that should work in older versions of Matlab:
tblread: output in terms of separate variables for strings and numbers
caseread: output in terms of a char array
tdfread: output in terms of a struct
Alternatively, textscan should be able to accomplish what you need and probably will be the fastest:
fid = fopen('data.txt');
header = textscan(fid,'%s',3); % Optionally save header names
C = textscan(fid,'%s%d%s','HeaderLines',1); % Read data skipping header
fclose(fid); % Don't forget to close file
C{:}
Found a way to solve my problem.
Because I don't have the latest version of MATLAB and cannot use readable which would be the preferred option I ended up doing using textread and specifying the format of each column.
Tedious but maybe the "simplest" way I could find:
[picFile subCode gender]=textread('data.txt', '%s %f %s', 'headerlines',1);
T=[picFile(:) subCode(:) gender(:)]
The textscan solution by #horchler seems pretty similar. Thanks!
I have a data file having 50 2-D data points written in Notepad. I want to use it in clustering algorithm to cluster these 50 points. How can I import this file? Is there any other way to use it in program?
You can save the data as a .csv file or you can save it to an excel spreadsheet and use xlsread(). See here for more info: http://www.mathworks.com/help/techdoc/ref/xlsread.html
For the .csv case, this post should prove helpful: Fastest way to import CSV files in MATLAB
Imagine you had the following data:
X = [randn(100,2)-1 ; randn(100,2)];
save data.mat X
Then its as simple as doing:
%# load data from MAT-file
load data.mat
%# cluster into K=2 clusters
C = kmeans(X,2);
%# show cluster assignment
gscatter(X(:,1), X(:,2), C)
It depends how you have formatted the data file. You say it is saved on notepad but that is not too helpful. Depending on what you have used as the data delimiter you can import the datafile into an array using the dlmread function. For example if your file is called filename.dat and have used a ; character to separate each data item within this file you could read the data into a matrix A using
A = dlmread("filename.dat",';');
I would suggest reading the help documentation on the dlmread function in matlab.
My raw CSV file looks like the 1st pic. And I wants to use Matlab read it into the format as the 2rd pic. I have over 1000 the same kind of CSV files, it will be painful if I do it by copy/paste. How can I do this? Any examples?
raw data:
output data:
First thing to realize is that a .csv file has a very simple format. Your above file is actually a plain text file with the following text on each line:
id,A001
height
a1,a2,a3
3,4,5
3,4,5
6,7,5
weight
a1,a2,a3
4,4,5
5,4,6
i6,7,5
So it is not all that hard for you to write your own parser in Matlab. You want to use commands like
fid = fopen('filename.csv','r');
L = fgetl(fid); % get a text line from the file
commas = find(L==','); % find where the commas are in the line
n1 = str2num(L(1:commas(1)-1); % convert the first comma-delimited number on line L
fidout - fopen('myfile.csv','w');
Lout = [ L(commas(2)+1:commas(3)-1) ', a1, a1'];
fwrite(fidout,Lout); % write a line out to the output file
fclose all; % close all open files.
It will seem slow at first reading the various values in to various variables, and then arranging them to write out the way you want them written out to your output file. But once you get rolling it will go pretty fast and you will find yourself with a pretty good understanding of what is in files, and you will know first hand what is involved in writing something like texscan.m or csvwrite.m and so on.
Good luck!