I opened a File in Matlab using the a+ permission to read and write, and append data to end of file. I am able to write and append data to the file properly, but I am not able to read.
Though the file permission definition says reading and writing, I am not able to read. Can you please help me here? Anybody encountered this problem?
fid = fopen('E:\code folder\Translation values.txt','a+')
[Array] = fscanf(fid,'%f %f')
The array returned is empty. same is the problem with textscan as well. The Cell array is empty. But when I change the permission to r+, it works fine. Please help me.
The flag a+ stands for "append and read", thus, the file position indicator pointer probably points to the end of the file. If so, you might need to call fseek or frewind before reading.
Related
Is there any way to create an empty .mat file from a terminal session? Basically, what I am doing is brain graph analysis. The software I am using, if an entire brain is scrubbed (ie, if the displacement of the brain is greater than a certain threshold) the output file will be left out or will be very small. When analyzing, however, I need to be able to eliminate both subjects from the analysis if the entire brain is scrubbed/too much of the brain is scrubbed. To accomplish this, the easiest way would be to simply check the dimensions of the output file within matlab, and if they are below the arbitrary threshold I decide then both subjects will just be skipped over for analysis. The issue is, I can easily check if a file contains too few remaining frames, however, if the resulting file contains no frames, it will entirely just not exist. As the outputs are all sorted, the only thing I need to do is check consecutive files' dimensions, and if one of the files does not contain enough values, then I can simply skip over it entirely. Simply touching a blank file obviously will not work, since it will not contain any encoding. I hope this is a good explanation for my motivation to do this, and if any of you know of any suggestions, please let me know.
A simple solution would be to create an empty file from Matlab and duplicate the file when needed from the console.
Just open Matlab, set to the destination folder and type this:
clear all
save empty.mat
Then, when needed, copy the file from the console. :)
Saving the contents of an empty struct creates an empty .mat file:
emptyStruct = struct;
save('myFile.mat','-struct','emptyStruct');
I have a MATLAB script that I could have sworn worked fine the last time I used it (a year ago). Now, I get this error:
Invalid file identifier. Use fopen to generate a valid file identifier.
If I understand correctly, it is failing to find or open(?) a file specified elsewhere in the script. Is this right? If so, what could cause it?
fid (file identifier) is the output of fopen. It's an integer, but not related to the file permanently. You need to use fopen to get the fid. It seems to me that you are using incorrect fid (file identifier) in some file-related I/O command, such as fread, fscanf or fclose. Unsuccessful fopen gives fid of -1. For any valid normal file successful fopen will give fid that is 3 or greater integer.
However, without any code it's impossible to say where or what the bug or error is. You could use MATLAB debugger to single-step the code from relevant fopen (set breakpoint there and run your program) until the relevant fclose and see if fid (or whatever variable name you use for file identifier) or any data structure for your file identifiers (if have more than one file identifier in your code) changes in any point between relevant fopen and fclose.
I solved this problem for my self by adding permission option to fopen.
As you see in http://www.mathworks.se/help/matlab/ref/fopen.html , fopen syntax is:
fileID = fopen(filename,permission)
Possible permissions, for example are:
'r' (default) | 'w' | 'a' | 'r+' | 'w+' | 'a+' | ...
'r' – Open file for reading.
'w' – Open or create new file for writing. Discard existing contents, if any.
'a' –
Open or create new file for writing. Append data to the end of the file.
'r+' – Open file for reading and writing.
'w+' – Open or create new file for reading and writing. Discard existing contents, if any.
'a+' – Open or create new file for reading and writing. Append data to the end of the file.
...
If I use fopen without permission option, or if I use 'r' (default) option, fopen will return -1, which is error. I success with this:
fid=fopen('tmp.txt', 'w');
fid=fopen('tmp.txt', 'a');
I had this problem. It turned out that the file I was trying to write was too large (I didn't have enough free space to accommodate it). However, the program didn't fail until the call to fclose. Very confusing!
Try freeing up some space, or writing a very small file, to test this diagnosis.
I encountered the same problem when trying to open ASF toolbox demos. Running Matlab as an administrator(right-click to open) seemed to solve this issue for me.
fopen can fail because MATLAB doesn't have the permissions to read/write the file you've specified.
Try opening a file in a location where you/MATLAB have all the rights (depending on your OS).
I have used fopen with permission and the same error came out. However, I started MATLAB as admin and that took care of the problem.
I had the file opened in excel and as a result fopen returned a -1.
Took me forever to find such a trivial problem.
It also happens when trying to create a file in a non-existent directory. Try mkdir('folderName') within MATLAB or just create the directory beforehand.
The path with a forward slash at the beginning can cause the same error.
filename = '/data/myfile.txt';
throws this error, while
filename = 'data/myfile.txt';
does not produce an error.
For my situation, I have checked everything, but missed an easy step.
Please select "browse your folder" and browse for your current document location before you run your 'fopen' code.
It also occurs when a script is trying to read beyond the end of the file.
I'm having troubles opening a file with different fid that is previously opened with 'Input'.
Example:
fid1=fopen((input('Video: ')),'r');
fid2=fopen((input('Save as: ')),'w');
...
...
fid3=fopen('','r'); % Here I want to open the input video same as fid1
I don't know how to request returned value, in this case the name entered.
Entering fid3=fid1 after declaration of fid1 does not help me.
I don't want to ask for the name to be input again (I.e fid3=fopen((input('Video: ')),'r');).
To do what you want to do, you need to capture and store the filename somewhere. I really don't think that information can be recovered from a file pointer.
This is a script written by someone else, and I don't understand why it is giving me this error (I don't really know Matlab, but this appears to be a fairly straightforward script, so I'm a bit stumped).
The file starts with
clear all
filein=['Runs/'];
Namein1=['AIC'];
Nameout=['Nash'];
It then does a bunch of calculations to get Nash-Sutcliffe coefficients (not important for this issue) and then tries to write the results to one file:
%Write Nash
%Output file writing
%Write file header
D={'Conbination','Nash with Error','Nash-error','RMSE','RMSE-error',...
'AIC', 'MinNash', 'MaxNash'};
NameOut=[filein,Nameout, '.txt'];
fileID = fopen(NameOut,'w');
for i=1:length(D)-1
fprintf(fileID,'%s\t',D{i});
Then more stuff follows, but this is where I get the error message:
Error using fprintf
Invalid file identifier. Use fopen to generate a valid file identifier.
Error in Nash_0EV_onlyT (line 169)
fprintf(fileID,'%s\t',D{i});
I don't get what is wrong here? The script specifies the file, and uses fopen...? Isn't it supposed to create the file Nash.txt with the fopen statement (this file currently does not exist in my folder Runs/)? What am I missing? Thanks!
PS I am running Matlab2013a (group license via the university) on a MacBook Pro with OSX 10.8
Try using fclose all before calling this script again. Often when testing, the file handle is never released (an error occurs before the file is closed), causing fopen on the same file to fail.
The better way to do this would be to use a more fail-safe construct:
NameOut = [filein Nameout '.txt'];
fileID = fopen(NameOut,'w');
if fileID > 0
try
for i = 1:length(D)-1
fprintf(fileID,'%s\t',D{i});
end
fclose(fileId);
catch ME
fclose(fileId);
throw(ME);
end
else
error('Error opening file.');
end
I am running Win 10 and matlab 2015a, but it happens in mine too.
finally, I realise that the matlab.exe can't write file in the folder /../bin/
so, change to
Nameout=['C:\Users\yourname\DesktopNash'];
try it, then tell me what' going on.
Okay, so as I said, I don't know Matlab... I hadn't properly specified the path for writing! So it was reading the input but I guess didn't know where to write to. Thanks for the answers, it did help me narrow down the problem!
I have a MATLAB script that I could have sworn worked fine the last time I used it (a year ago). Now, I get this error:
Invalid file identifier. Use fopen to generate a valid file identifier.
If I understand correctly, it is failing to find or open(?) a file specified elsewhere in the script. Is this right? If so, what could cause it?
fid (file identifier) is the output of fopen. It's an integer, but not related to the file permanently. You need to use fopen to get the fid. It seems to me that you are using incorrect fid (file identifier) in some file-related I/O command, such as fread, fscanf or fclose. Unsuccessful fopen gives fid of -1. For any valid normal file successful fopen will give fid that is 3 or greater integer.
However, without any code it's impossible to say where or what the bug or error is. You could use MATLAB debugger to single-step the code from relevant fopen (set breakpoint there and run your program) until the relevant fclose and see if fid (or whatever variable name you use for file identifier) or any data structure for your file identifiers (if have more than one file identifier in your code) changes in any point between relevant fopen and fclose.
I solved this problem for my self by adding permission option to fopen.
As you see in http://www.mathworks.se/help/matlab/ref/fopen.html , fopen syntax is:
fileID = fopen(filename,permission)
Possible permissions, for example are:
'r' (default) | 'w' | 'a' | 'r+' | 'w+' | 'a+' | ...
'r' – Open file for reading.
'w' – Open or create new file for writing. Discard existing contents, if any.
'a' –
Open or create new file for writing. Append data to the end of the file.
'r+' – Open file for reading and writing.
'w+' – Open or create new file for reading and writing. Discard existing contents, if any.
'a+' – Open or create new file for reading and writing. Append data to the end of the file.
...
If I use fopen without permission option, or if I use 'r' (default) option, fopen will return -1, which is error. I success with this:
fid=fopen('tmp.txt', 'w');
fid=fopen('tmp.txt', 'a');
I had this problem. It turned out that the file I was trying to write was too large (I didn't have enough free space to accommodate it). However, the program didn't fail until the call to fclose. Very confusing!
Try freeing up some space, or writing a very small file, to test this diagnosis.
I encountered the same problem when trying to open ASF toolbox demos. Running Matlab as an administrator(right-click to open) seemed to solve this issue for me.
fopen can fail because MATLAB doesn't have the permissions to read/write the file you've specified.
Try opening a file in a location where you/MATLAB have all the rights (depending on your OS).
I have used fopen with permission and the same error came out. However, I started MATLAB as admin and that took care of the problem.
I had the file opened in excel and as a result fopen returned a -1.
Took me forever to find such a trivial problem.
It also happens when trying to create a file in a non-existent directory. Try mkdir('folderName') within MATLAB or just create the directory beforehand.
The path with a forward slash at the beginning can cause the same error.
filename = '/data/myfile.txt';
throws this error, while
filename = 'data/myfile.txt';
does not produce an error.
For my situation, I have checked everything, but missed an easy step.
Please select "browse your folder" and browse for your current document location before you run your 'fopen' code.
It also occurs when a script is trying to read beyond the end of the file.