In MATLAB:
I have this independent function which runs optimal in the command line:
function datacollect()
filename = uigetfile('*.txt')
[col] = importdata(fileName)
long = columns(:,1)
lat = columns(:,2)
handles.long = long;
handles.lat = lat;
But when I make a function call inside GUIDE:
datacollect()
I get an error:
??? Reference to non-existent field 'output'.
My guess is that there is a name collision between the handles variable in GUIDE that is being used for saving graphics handles and other data, and the one that your function uses.
Try to rename handles in your function to something else, and run again.
Related
I am attempting to create a MATLAB app that saves the specific fields in a .mat file and allows for custom naming. Saving has seemed to work however attempting to load leads to nothing changing.
Any help would be appreciated
function SaveButtonPushed(app, event) % Saving element
props = properties(app);
lp = length(props);
values = cell(1,lp);
visibilities = cell(1,lp);
for i = 1:lp
propName = props{1};
property = app.(propName);
if isprop(property, 'Value')
values{i} = app.(propName).Value;
end
% if isprop(property, 'Visible')
% visibilities{i} = app.(props{i}).Visible;
% end
end
file = uiputfile('*.mat', "Save Message" );
if file
save(file, 'props', 'values', 'visibilities');
end
end
function LoadButtonPushed(app, event) % Loading element
[file,path] = uigetfile('*.mat');
selectedfile = fullfile(file);
load(selectedfile)
end
It is like Wolfie said in his comment. The variables in the .mat file are loaded into the private workspace for that function, which is cleared at once it exits.
So within the function you should be able to loop over your app properties again and set the values the ones loaded from the file.
Note that if you add a breakpoint, as Wolfie says, you should be able to see the private workspace and your loaded variables will be there until the function exits.
Alternatively, you could load the variables in to a structure:
S = load(selectedfile);
(See https://uk.mathworks.com/help/matlab/ref/load.html for more details)
and return that structure,
function [S] = LoadButtonPushed(app, event) % Loading element
You will have to change the interface/load function call to accept the returned variable, and I'm not sure that you can add the contents of the structure to the global namespace. However, you can access them through the loaded structure as:
S.props
I wanted to ask how values in MATLAB are returned? Are they copied or passed by reference?
take a look at this example with matrix A:
function main
A = foo(10);
return;
end
function [resultMatrix] = foo(count)
resultMatrix = zeros(count, count);
return;
end
Does the copy operation take place when function returns matrix and assigns it to variable A ?
MATLAB uses a system known as copy-on-write in which a copy of the data is only made when it is necessary (i.e. when the data is modified). When returning a variable from a function, it is not modified between when it was created inside of the function and when it was stored in a different variable by the calling function. So in your case, you can think of the variable as being passed by reference. Once the data is modified, however, a copy will be made
You can check this behavior using format debug which will actually tell us the memory location of the data (detailed more in this post)
So if we modify your code slightly so that we print the memory location of each variable we can track when a copy is made
function main()
A = foo(10);
% Print the address of the variable A
fprintf('Address of A in calling function: %s\n', address(A));
% Modify A
B = A + 1;
% Print the address of the variable B
fprintf('Address of B in calling function: %s\n', address(B));
end
function result = foo(count)
result = zeros(count);
% Print the address of the variable inside of the function
fprintf('Address of result in foo: %s\n', address(result));
end
function loc = address(x)
% Store the current display format
fmt = get(0, 'format');
% Turn on debugging display and parse it
format debug
loc = regexp(evalc('disp(x)'), '(?<=pr\s*=\s*)[a-z0-9]*', 'match', 'once');
% Revert the display format to what it was
format(fmt);
end
And this yields the following (or similar) output
Address of result in foo: 7f96d9d591c0
Address of A in calling function: 7f96d9d591c0
Address of B in calling function: 7f96d9c74400
As a side-note, you don't need to explicitly use return in your case since the function will naturally return when it encounters the end. return is only necessary when you need to use it to alter the flow of your program and exit a function pre-maturely.
I want to find the Minimum of a function using
[x,fval] = fminsearch(#(param) esm6(param,identi),result(k,1:end-1),options)
now for each Iteration step i want some values that the function 'esm6' calculates to be saved in an Array. I tried the following:
In the first line of the function i wrote
identi.sim.i_optiIter = identi.sim.i_optiIter + 1;
to have an iteration-variable counting the iteration steps of fminsearch. And later to catch the values that I need I used
identi.sim.guete_werte.gew(identi.sim.i_optiIter,:,:) = y_sim;
identi.sim.guete_werte.ungew(identi.sim.i_optiIter,:,:) = y_sim_ungew;
and to make sure that I use the new values of the identi-struct for the next function call, I wrote this at the end of the function:
assignin('base','identi',identi);
Now unfortunatly it doesn't do what I wanted it to do. Can anyone help me with this?
EDIT:
I made another attempt on it, using an Output function. I extendend my Options like this:
options = optimset('Display','iter','MaxIter',3,'OutputFcn',#outfun);
But now the Problem is that i cannot figure out where to put this outfun. The outfun Looks like this:
function stop = outfun(x,optimvalues,state,iteration,y_sim,y_sim_ungew)
stop = false;
if state == 'iter'
guete_werte.gew(iteration,:,:) = y_sim;
guete_werte.ungew(iteration,:,:) = y_sim_ungew;
end
end
Now the Problem with it is, that i can not put it in the file, where i call the fminsearch, because that is a script. If i put the outputfunction into a separate .m-function file, it is not able to Access the variables of the esm6 function. And if I add it to the esm6-function file, matlab can't find the function and says
??? Error using ==> feval Undefined function or method 'outfun' for
input arguments of type 'struct'.
I have a function but I cannot deal with the variable named data when I call the function. If I run the code alone (without calling the function, it works).
Please find the actual code below:
function data = returns_ext(input);
clear all
clc
ticker = 'BA';
filename = ['C:\Users\FP\Documents\MatlabCode\P\prices\' ticker 'daily.csv'];
newData1 = importdata(filename);
% Create new variables in the base workspace from those fields.
vars = fieldnames(newData1);
for i = 1:length(vars)
assignin('base', vars{i}, newData1.(vars{i}));
end
prices_data = data;
ERROR: At compilation, "data" was determined to be a variable and this
variable is uninitialized. "data" is also a function name and previous versions of MATLAB would have
called the function.
However, MATLAB 7 forbids the use of the same name in the same
context as both a function and a variable.
Error in ==> returns_ext at 17
prices_data = data;
You should replace assignin by eval, since assignin assigns either in the caller function calling returns_ext or the base workspace. See the simple example below:
function test
newData1.prices = 1;
newData1.dates = 2;
variables = {'prices','dates'};
for i = 1:length(variables)
temp = newData1.(variables{i});
eval([variables{i} ' = temp;']);
end
disp(prices)
disp(dates)
If the data is available in 'base' workspace then you need to update your code as this:
data = eval('base','data;');
prices_data = data;
I have a set of code that, depending on how the program is initiated, will either be executed locally or sent to a remote machine for execution. The ideal way I imagine this could work would look something like the following:
line_of_code = 'do_something_or_other();';
if execute_remotely
send_via_udp(line_of_code);
else
eval(line_of_code);
end
The thing is, I know that the eval() function is ridiculously inefficient. On the other hand, if I write out line_of_code in each section of the if block, that opens the door for errors. Is there any other way that I can do this more efficiently than by simply using eval()?
EDIT: After more consideration and some discussion in the comments, I have my doubts that function handles can be transmitted via UDP. I'm therefore updating my answer, instead suggesting the use of the function FUNC2STR to convert the function handle to a string for transmission, then using the function STR2FUNC to convert it back to a function handle again after transmission...
To get around using EVAL, you can use a function handle instead of storing the line of code to be executed in a string:
fcnToEvaluate = #do_something_or_other; %# Get a handle to the function
if execute_remotely
fcnString = func2str(fcnToEvaluate); %# Construct a function name string
%# from the function handle
send_via_udp(fcnString); %# Pass the function name string
else
fcnToEvaluate(); %# Evaluate the function
end
The above assumes that the function do_something_or_other already exists. You can then do something like the following on the remote system:
fcnString = receive_via_udp(); %# Get the function name string
fcnToEvaluate = str2func(fcnString); %# Construct a function handle from
%# the function name string
fcnToEvaluate(); %# Evaluate the function
As long as the code (i.e. m-file) for the function do_something_or_other exists on both the local and remote systems, I think this should work. Note that you could also use FEVAL to evaluate the function name string instead of converting it to a function handle first.
If you need to create a function on the fly, you can initialize fcnToEvaluate as an anonymous function in your code:
fcnToEvaluate = #() disp('Hello World!'); %# Create an anonymous function
And the code to send, receive, and evaluate this should be the same as above.
If you have arguments to pass to your function as well, you can place the function handle and input arguments into a cell array. For example:
fcnToEvaluate = #(x,y) x+y; %# An anonymous function to add 2 values
inArg1 = 2; %# First input argument
inArg2 = 5; %# Second input argument
cellArray = {fcnToEvaluate inArg1 inArg2}; %# Create a cell array
if execute_remotely
cellArray{1} = func2str(cellArray{1}); %# Construct a function name string
%# from the function handle
send_via_udp(cellArray); %# Pass the cell array
else
cellArray{1}(cellArray{2:end}); %# Evaluate the function with the inputs
end
In this case, the code for send_via_udp may have to break the cell array up and send each cell separately. When received, the function name string will again have to be converted back to a function handle using STR2FUNC.