I have a variable that is holding a string (the string contains a path to a .mat file). However whenever I call load the variable I get an error saying "Error using load Unable to read file"
Here is my code where I call load:
fName = strcat(fName,'_features.mat');
display(fName);
load(fName);
For those curious fName = '/Users/MATLAB/10360453085_p2_features.mat'
Why am getting an error on load even though when I copy the value of fName into load it works perfectly fine, but using load(fName) gives me an error?
Most likely, fname is initialized somewhere as a cell array. strcat will therefore return a cell array, so that disp will display it as 'name' rather than name.
load(fName{1})
or
load(char(fName))
will work in this case.
Related
I have tried:
saveas(keys ,keyname);
save(keys ,keyname ,'-mat');
save(keys ,keyname);
where keys is a 3006x4104 matrix of the class double.
I tried to use some casting so I would save it as txt file
for keyname I tried - ./newdronephotos/1880key.mat
and newdronephotos/1880key.mat.
It's not working.
In particular, when I'm trying saveas(keys ,keyname);
it's starting to do some processes and then print the error message:
Error using saveas (line 88)
Simulink object array must be a vector
Actually, I just succeeded to solve my own problem.
The function save() expect to have a string of the name of the desired variable.
For example:
Instead of -
save(keyname ,keys);
I needed to write-
save(keyname ,'keys');
Warning: Direct access of structure fields returned by a function call (e.g.,
call to INPU) is not allowed. See MATLAB 7.10 Release Notes, "Subscripting Into Function Return Values" for details.
In Main at 3
??? Attempt to reference field of non-structure array.
Error in ==> Main at 3
INPU.m;
getting this error...how to call this inpu.m file.
my input file is below.
it reads data from dat file.
%---INPU.m----
%This file reads the input data from the file ‘‘'ex.dat'" and saves them in vector form
n=csvread('ex.dat',1,0,[1,0,1,0]);
constr=csvread('ex.dat',4,0,[4,0,4,(3*n-1)]);
q=csvread('ex.dat',7,0,[7,0,7,(3*(n+1)-1)]);
r=csvread('ex.dat',10,0,[10,0,10,(3*n-1)]);
x=csvread('ex.dat',13,0,[13,0,13,(3*n-1)]);
dx=csvread('ex.dat',16,0,[16,0,16,(3*n-1)]);
To call a function, you use it's name, not the filename (which has a .m file extension). The function name is the portion of the filename without the .m. In your case, since your function is saved in the file INPU.m, you just invoke it with INPU.
I am reading an input from a file and importing it into my data to run in Matlab:
parts = strread(tline,'%s','delimiter',';')
employee(i).name = parts(1);
employee(i).salary= str2double(parts(2));
Then I try to print it out:
for i = 1:3
fprintf('salary: %.2f\n',employee(i).salary);
fprintf('employee name: %s\n',employee(i).name);
end
The salary prints with no problem. But the for the variable "name" it gives an error:
Error using fprintf
Function is not defined for 'cell' inputs.
fprintf('employee name: %s\n',employee(i).name);
I looked for some other examples:
access struct data (matlab)
How do I access structure fields dynamically?
Matlab Error: Function is not defined for 'cell' inputs
How do i define a structure in Matlab
But there is nothing to address this case, where only string is not working.
I have not explicitly declared the data as struct, i.e. inside the code there is nowhere the "struct" word is included, but Matlab apparently automatically understand it as an "Array of structures".
Any hints what might be missing here?
All comments are highly appreciated!
The issue is that employee(k).name is a cell (check with iscell(employee(1).name)) and the format string %s doesn't know how to handle that.
The reason that it is a cell is because strread returns a cell array. To grab an element from the result (parts), you want to use {} indexing which returns a string rather than () which will return a cell.
employee(i).name = parts{1};
I have an FFT and I want to save this to .mat file and then read it from that .mat file. I want to use my loaded data for a division. Here is my code
save ('file_fft','a_fft');
b = load ('file_fft');
c = abs (d_fft) ./ abs (b);
In my command window I see that
b = file_fft [4000 * 1 double].
And then I get error message
'Undefined function 'abs' for input arguments of type 'struct''
I tried after deleting abs. I got this error
'Undefined function 'rdivide' for input arguments of type 'struct''
Does anybody have any idea that why it is not working and how i can solve it?
Check the documentation for the load function:
S = load(___) loads data into S, using any of the input arguments in
the previous syntax group.
If filename is a MAT-file, then S is a structure array.
If filename is an ASCII file, then S is a double-precision array
containing data from the file.
So b is a structure and as suggested in the comment, you need to access the data as abs(b.a_fft).
The problem is that load() already creates the file structure that is inside the .mat file. When you assign file_fft with load, it creates a struct.
From the documentation of load():
S = load(_) loads data into S, using any of the input arguments in
the previous syntax group.
If filename is a MAT-file, then S is a structure array.
Edit:
I got sniped :-P
Here's another working example of code:
save ('file_fft','a_fft');
load ('file_fft');
c = abs (d_fft) ./ abs (file_fft);
I am getting an error when running matlab code. Here I am trying to use one of the outputs of previous code as input to my new code.
??? Reference to non-existent field 'y1'.
Can anyone help me?
A good practice might be to check if the field exists before accessing it:
if isfield( s, 'y1' )
% s.y1 exists - you may access it
s.y1
else
% s.y1 does not exist - what are you going to do about it?
end
To take Edric's comment into account, another possible way is
try
% access y1
s.y1
catch em
% verify that the error indeed stems from non-existant field
if strcmp(em.identifier, 'MATLAB:nonExistentField')
fprintf(1, 'field y1 does not exist...\n');
else
throw( em ); % different error - handle by caller?
end
end
Have you used the command load to load data from file(s)?
if yes, this function overwrite your current variables, therefore, they become non-existent, so when you call, it instead of using:
load ('filename');
use:
f=load ('filename');
now, to refer to any variable inside the loaded file use f.varname, for
example if there is a network called net saved within the loaded data you may use it like:
a = f.net(fv);
I would first explain my situation and then give the solution.
I first save a variable op, it is a struct , its name is coef.mat;
I load this variable using coef = load( file_path, '-mat');
In a new function, I pass variable coef to it as a parameter, at here, the error Reference to non-existent field pops out.
My solution:
Just replace coef with coef.op, then pass it to the function, it will work.
So, I think the reason behind is that: the struct was saved as a variable, when you use load and want to acess the origin variable, you need point it out directly using dot(.) operation, you can directly open the variable in Matlab workspace and find out what it wraps inside the variable.
In your case, if your the outputs of previous code is a struct(It's my guess, but you haven't pointed out) and you saved it as MyStruct, you load it as MyInput = load(MyStruct), then when use it as function's parameter, it should be MyInput.y1.
Hops it would work!
At first load it on command window and observe the workspace window. You can see the structure name. It will work by accessing structure name. Example:
lm=load('data.mat');
disp(lm.SAMPLE.X);
Here SAMPLE is the structure name and X is a member of the structure