When I execute the following:
function [ x ] = addya( varargin )
x=varargin{1};
t=varargin{1};
if(nargin>1)
for i=2:nargin
t=t+varargin(i);
end;
end
x=t;
The error i am getting is:
addya(1,1) ??? Undefined function or method
'addya' for input arguments of type 'double'.
please suggest changes and errors.
Make sure this function is saved in a file called addya.m.
Moreover, as mentioned by il_raffa there's a typo - inside the loop: you should access varargin using {}.
The following code works for me when saved as addya.m:
function [ x ] = addya( varargin )
x=varargin{1}; %// Why is this needed?
t=varargin{1};
if(nargin>1)
for i=2:nargin
t=t+varargin{i};
end;
end
x=t;
Also, I would suggest to refrain from using i as a loop index due to possible complication with complex numbers.
Related
So, i have been doing this work with matlab and every time i try to get the answer a new problem pops up. The one that repeats the most on the prompt is
??? Input argument "x" is undefined.
The work is about deriving with matlab, i have to derive a function with two diferent derivation methods and i have to get that table. Thanks a lot to everyone that trys to answer im very lost with this subject.
clc,clear;
h=1;
x=1.2;
derivada1=derivada_1(x,h);
derivada2=derivada_2(x,h);
for i=0:1:10
fprintf('%.10f %.10f %.10f\n',h*(10.^(-i)),derivada1,derivada2);
end
The function i have to derive is
function [ fx ] = funcion( x )
%UNTITLED2 Summary of this function goes here
% Detailed explanation goes here
fx=x.^3-3*x.^2-x+3;
end
Method1
function [ dfx1 ] = derivada_1( x,h )
%UNTITLED4 Summary of this function goes here
% Detailed explanation goes here
fx=feval(funcion,x);
fh2=feval(fx,x+h);
fh3=feval(fx,x-h);
dfx1=(fh2-fh3)/(2*h);
end
Method 2
function [ dfx2 ] = derivada_2( x,h )
%UNTITLED4 Summary of this function goes here
% Detailed explanation goes here
fx=feval(funcion,x);
fh1=feval(fx,x+2*h);
fh2=feval(fx,x+h);
fh3=feval(fx,x-h);
fh4=feval(fx,x-2*h);
dfx2=(-fh1+8*fh2-8*fh3+fh4)/(12*h);
end
Code
Table of results
You really over-complicated it using feval, it's that simple:
function [ dfx1 ] = derivada_1(x,h )
fh2=funcion(x+h);
fh3=funcion(x-h);
dfx1=(fh2-fh3)/(2*h);
end
The problem with your original code was you didn't use function handles. feval(funcion,x) evaluates funcion and passes the returned values to feval, but funcion requires input arguments. Instead it should be something like feval(#funcion,x) passing a function handle (aka function pointer in other programming languages).
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 am writing MATLAB code that will fit together with other MATLAB functions that I cannot modify. Some of these existing functions take input from the command line. Is there a way I can write a test script in MATLAB that can call these functions, and then provide the input as the user would?
ie. if I have a function:
function y = f(x)
z = input('Enter number: ');
y = x + z;
end
Is there a way to have a script call f and provide z?
If you are looking for a non elegant solution.
If you are looking for a potentially dangerous solution.
Then you might try this: write a function named "input" as follows:
function a=input(str)
% THIS IS THE DUMMY VERSION OF THE
% MATLAB BUILT-IN FUNCTION "input"
global dummy_input
disp('WARNING!!!')
disp('MATLAB "input" built-in function overridded')
disp(['Setting dummy_inpt'])
a=dummy_input;
end
Declare a global variable either in the script you use to test the function and in your "dummy" input function.
Assign the desired value to the global variable as follows:
global dummy_input
x=3;
dummy_input=123;
y=my_func(x)
dummy_input=42.13;
y=my_func(x)
If my_func is the function you post in the question, you will obtain:
WARNING!!!
MATLAB "input" built-in function overridded
Setting dummy_inpt
y =
126
WARNING!!!
MATLAB "input" built-in function overridded
Setting dummy_inpt
y =
45.1300
I've added the printing of the warnings in the "dummy" input function yust as a remainder ...
You do not need to modify the function you want to test, when it will call input to get a number from the user, it will call your "dummy" input.
Version 2 of the "dummy" input function
This version of the "dummy" input function allows autonatically handling multiple request of input values.
It requires the user knows in advance how many times the "original" input function is called.
No additional global counter is required.
It is sufficient the change the definition of the global parameter in the script, declaring it as an array containing the set of input the user want to assign:
global input_list
input_list=[27 30 5 31 21]
In the "dummy" input function, the first element of the array is assigned to the output variable, then the it is deleted:
a=input_list(1);
input_list(1)=[];
the code of the updated version of the function is the following:
function a=input(str)
% THIS IS THE DUMMY VERSION OF THE
% MATLAB BUILT-IN FUNCTION "input"
global input_list
disp('WARNING!!!')
disp('MATLAB "input" built-in function overridded')
disp(' ')
disp(' ')
disp(' ')
if(isempty(input_list))
error('Error in DUMMY input: no more input data')
else
disp(['Setting dummy_input ' num2str(input_list(1))])
a=input_list(1);
disp(' ')
disp(' ')
disp(' ')
input_list(1)=[];
end
end
An error is generated in case the input array becomes empty (by deleting its element at each call) before the end of the script.
I've also added some calls to disp to make more "clear" the output on the Command Window.
Also the "dummy" input function print a message on the Command Window telling which input values has been assigned.
Make sure to remove your dummy "input" function at the end
Hope this helps.
I am trying to made my own Matlab function to use in Simulink but I have not success. It is a simple If statement with one input and three output values,all of them integer, here the code:
function [ PWM,INA,INB ] = VNH5019(in_Motor)
if in_Motor ==0
INA=0;
INB=0;
PWM=0;
elseif in_Motor>0
if in_Motor>255
in_motor=255;
end
INA=1;
INB=0;
PWM=in_Motor;
elseif in_Motor<0
if in_Motor<-255
in_motor=-255;
end
INA=0;
INB=1;
PWM=-in_Motor;
end
And here the error:
Output argument 'PWM' is not assigned on some execution paths.
Function 'MATLAB Function' (#38.28.35), line 1, column 29:
"VNH5019"
You should probably replace that line:
elseif in_Motor<0
with a simple else.
Try to assing a value to the variables before the ifs. Simulink needs values to be always defined in this type of block functions and it seems that in yours they are, but the compiler thinks they are not. So before any if, asign some value to your outputs.
It will probably work.
I am trying to write a minimal function that can be called with a variable number of arguments but that will not throw a wrong number of arguments error if miscalled.
Here is where I start from :
function varargout=fname(varargin)
% FNAME
% Usage: output=fname(input)
% Arguments check
if(nargin~=1 || nargout~=1)
disp('Function fname requires one input argument');
disp('and one output argument');
disp('Try `help fname`');
varargout(1:nargout)={0};
return;
end
input=varargin{1};
output=input;
varargout(1)={output};
end
However this does not work as I would like it to. Is there a way to write a function that :
never throw a "wrong number of arguments" error (so that the rest of the execution can continue)
accepts variable number of input and output arguments and checks them inside the function
(maybe more tricky) if the number of input / output arguments is not correct, does not replace the value of the provided output arguments (so that any misplaced call does not erase the previous value of the output argument)
I am open to any suggestions / other methods.
Thank you for your help.
UPDATE: thanks to #Amro for his answer, I guess what I miss here is either a call by address of reference for Matlab functions or a way to interrupt a function without returning anything and without stopping the rest of the execution.
Here is one way to implement your function:
function varargout = fname(input,varargin)
%# FNAME
%# Usage: output=fname(input)
%%# INPUT
if nargin<1
varargout(1:nargout) = {[]};
warning('Not enough input arguments.'), return
end
if ~isempty(varargin)
warning('Too many input arguments.')
end
%%# YOUR CODE: manipulate input, and compute output
output = input;
%%# OUTPUT
varargout{1} = output;
if nargout>1
warning('Too many output arguments.')
varargout(2:nargout) = {[]};
end
end
Obviously you can customize the warning messages to your liking...
Also, if you want your function to simply print the message instead of issuing warnings, replace all WARNING calls with simple DISP function calls.
Examples of function call:
fname()
fname(1)
fname(1,2)
x = fname()
x = fname(1)
x = fname(1,2)
[x,y] = fname()
[x,y] = fname(1)
[x,y] = fname(1,2)
The above calls execute as expected (showing warning messages when applicable). One caveat though, in the last three calls, if the variable y already existed in the workspace prior to the calls, it would be overwritten by the empty value y=[] in each...
If I understand your question correctly, then the answer is no. If a caller calls a function like this:
[a, b, c] = fname('foo');
then fname is required to return (at least) three outputs. There's no way to tell MATLAB that it should leave b and c alone if fname only returns one output.