I have different mat files w/ distinct names. So I am using a function whose input is the mat file. I used "varargin" to enable the function to take different files.
function bestfunc(varargin)
data = load(varargin, '-mat');
end
when I try to call the function like
bestfunc('matrix777')
Matlabe comes up w/ this error:
Error using load
Argument must contain a string.
Any ideas?
you have to get the names of the files. You can use dir() to do that.
dir('*.mat') % will return information about all .mat files in the folder
The output is a struct with more information for each file. TO get the names try
names=struct2cell(dir('*.mat'));
names=names(1,:);
now names is a cellarray with the names of all *.mat files of your folder. TO load data from each go for
for i=1:length(names)
bestfun(names{i});
end
Since you're only passing one argument, you don't need varargin, which is used when you may have a variable number of arguments to a function.
Just use a normal variable name like matname:
function bestfunc(matname)
data = load(matname, '-mat');
end
Then call it as you did before:
bestfunc('matrix777')
Related
i have a directory that includes some .mat files , i want to load all these files into an array .
i tried something like this :;
x1=load('C:\Users\me\OneDrive\Desktop\project\a\first_file.mat')
x2=load('C:\Users\me\OneDrive\Desktop\project\a\second_file.mat')
... and so on for all the files in the directory , and at the end i want to have an array such that:
arr(1)=x1 ...
how can i access the directory and load all of the files at the same time into an array ?
ps: i tried using path before and dir but then i got this error :
error using eval , undefind function 'workspacefun' for input
arguments of type struct
thank you in advance.
The load function loads what variables are in the .mat file with their real names into the current workspace. If you assign x as an output for load, the variables names appear as fields of a struct named x. For example, if first.mat contains v1, then, x = load('first.mat') will result in a x = struct with fields: v1.
So, in your case, assuming that you are sure that each .mat file contains a single variable, you can write the following loop to load all .mat files into a cell array arr.
fds = fileDatastore('*.mat', 'ReadFcn', #load); % assume same folder
files = fds.Files;
for i = 1:length(files)
% convert one-field struct into array, store in "arr"
arr{i} = struct2array(load(files{i}));
end
And each arr{i} will now contain a variable, say vi, in lexicographic order. If the .mat file contains more than one variable, this code will break. If the files are in another folder, you can use their actual path and extension like this fileDatastore('path', 'ReadFcn', #load, 'FileExtensions','.mat').
I'm trying to save list of variables from the workspace into a .mat file. The problem I encountered is that I'm trying to make a function of it, and that function should be able to handle a list of variables to be saved. I could loop as below:
vars = {'a','b','c'}; % names of variables
for k = 1:numel(vars)
save(filename,vars(k),'-append');
end
but this is not elegant for me and the flag -append slowed down the process.
I'm trying to achieve something like this:
vars = {'a','b','c'}; %names of variables
save(filename,vars);
Is this possible?
Since save expects each variable name as a separate input argument, you can use a comma-separated list generated from the cell array:
save(filename, vars{:})
There are two parts of my query
1) How to save different fields of structures as separate files(each file containing only named field of structure )?
2) Forcing save command to create directories in the save path when intermediate directories do not exist?
For first part:
data.a.name='a';
data.a.age=5;
data.b.name='b';
data.b.age=6;
data.c.name='c';
data.c.age=7;
fields=fieldnames(data);
for i=1:length(fields)
save(['E:\data\' fields{i} '.mat'],'-struct','data');
end
I want to save each field of struct data as a separate .mat file. So that after executing the loop, I should have 3 files inside E:\data viz. a.mat,b.mat and c.mat and a.mat contains only data of field 'a', b.mat contains only data of field 'b' and so on.
When I exeucte the above code, I get three files in my directory but each file contains identical content of all three variables a, b and c, instead of individual variables in each file.
Following command does not work:
for i=1:length(fields)
save(['E:\data\' fields{i} '.mat'],'-struct',['data.' fields{i} ]);
end
Error using save
The argument to -STRUCT must be the name of a scalar structure variable.
Is there some way to use save command to achieve my purpose without having to create temporary vaiables for saving each field?
For Second Part:
I have large number of files which need to stored in a directory structure. I want following to work.
test='abcdefgh';
save(['E:\data\' test(1:2) '\' test(3:4) '\' test(5:6) '\result.mat'])
But it showing following error
Error using save
Cannot create 'result.mat' because 'E:\data\ab\cd\ef' does not exist.
If any intermediate directory are not present, then they should be created by save command. I can get this part to work by checking if directory is present or not using exist command and then create directory using mkdir. I am wondering if there is some way to force save command to do the work using some argument I am not aware of.
Your field input argument to save is wrong. Per the documentation, the format is:
'-struct',structName,field1,...,fieldN
So the appropriate save syntax is:
data.a.name='a';
data.a.age=5;
data.b.name='b';
data.b.age=6;
data.c.name='c';
data.c.age=7;
fields = fieldnames(data);
for ii = 1:length(fields)
save(['E:\data\' fields{ii} '.mat'], '-struct', 'data', fields{ii});
end
And no, you cannot force save to generate the intermediate directories. Check for the existence of the save path first and create it if necessary.
I am creating a matlab application that is analyzing data on a daily basis.
The data is read in from an csv file using xlsread()
[num, weather, raw]=xlsread('weather.xlsx');
% weather.xlsx is a spreadsheet that holds a list of other files (csv) i
% want to process
for i = 1:length(weather)
fn = [char(weather(i)) '.csv'];
% now read in the weather file, get data from the local weather files
fnOpen = xlsread(fn);
% now process the file to save out the .mat file with the location name
% for example, one file is dallasTX, so I would like that file to be
% saved as dallasTx.mat
% the next is denverCO, and so denverCO.mat, and so on.
% but if I try...
fnSave=[char(weather(i)) '.mat'] ;
save(fnSave, fnOpen) % this doesn't work
% I will be doing quite a bit of processing of the data in another
% application that will open each individual .mat file
end
++++++++++++++
Sorry about not providing the full information.
The error I get when I do the above is:
Error using save
Argument must contain a string.
And Xiangru and Wolfie, the save(fnSave, 'fnOpen') works as you suggested it would. Now I have a dallasTX.mat file, and the variable name inside is fnOpen. I can work with this now.
Thanks for the quick response.
It would be helpful if you provide the error message when it doesn't work.
For this case, I think the problem is the syntax for save. You will need to do:
save(fnSave, 'fnOpen'); % note the quotes
Also, you may use weather{i} instead of char(weather(i)).
From the documentation, when using the command
save(filename, variables)
variables should be as described:
Names of variables to save, specified as one or more character vectors or strings. When using the command form of save, you do not need to enclose the input in single or double quotes. variables can be in one of the following forms.
This means you should use
save(fnSave, 'fnOpen');
Since you want to also use a file name stored in a variable, command syntax isn't ideal as you'd have to use eval. In this case the alternative option would be
eval(['save ', fnSave, ' fnOpen']);
If you had a fixed file name (for future reference), this would be simpler
save C:/User/Docs/MyFile.mat fnOpen
I have 31 models an I want to save each one in a specific file
this is my matlab function
formatspec='model%d'
for k = 1:length(libsvmFiles)
baseFileName = libsvmFiles(k).name;
fullFileName = fullfile(myFolder, baseFileName);
[labels train]=libsvmread(fullFileName);
model=svmtrain(labels,train, '-t 2 -h 0');
file=sprintf(formatspec,k);
save file model;
but the problem is only the first file is saved and its name is 'file' tha's mean the value of the variable file is not evaluated
how can I solve this problem ?
As many Matlab functions, save can be used in function form (save(...)) or in command form (save ...). In the command form that you use, all the arguments are interpreted as strings. That means
save file model
is equivalent to
save('file', 'model')
For the second argument that is correct, because you want to refer to the variable with the name "model". For the first argument it is wrong, because you want to refer to the file name contained in the variable file. The correct syntax to use is therefore
save(file, 'model')
You're missing the parens for the save function. The model variable also needs to be listed as a string since you need to tell the save function the name of the variable, not the variable itself. See Matlab's documentation.
save(file, 'model');
Additionally you don't have an end to your for loop shown, which normally would just throw an error -- however later code might cause this loop to instead only run once. Otherwise you should check your libsvmFiles variable as it might be only length 1 or not be an array.