I have code which is in multiple function files, input to these functions are stored in one file called inputfile.m(script file), in which I assigned some constant values to the inputs. These values act as a input to several function files named degree_eq.m(function file).
How I can write the code so that every time of execution, function files takes the required inputs from the inputfile.m.
Let's say you have two functions, one with your inputs (inputfile) and one where you do stuff (do_stuff).
function [a,b,c] = inputfile()
%define your constants
a=10;
b=100;
c=8.3;
function z = do_stuff()
[a, b, c] = inputfile() %takes the inputs from inputfile.m
z = a*c - b;
You can exploit the fact that matlab variables are persistent outside their scope. Lets say you have 6 constants a,b,c,d,e,f defined in input file. So what can be done is, write a top script called top.m which would be something like
inputfile
degree_eq1(a,b,c)
degree_eq2(c,d,e)
A third approach (combining Nirvedh Meshram and qbzenker answers) is to call an input script inside your MATLAB functions.
The advantage is that you do not have to specify which parameters are needed from or specified in your input script, but this is a disadvantage too, because the needed inputs are not made explicit. So, it is much more error prone. I only recommend this approach for a large number of input variables.
inputfile.m:
a = 5;
b = 8;
c = 10;
degree_eq.m:
function d = degree_eq()
inputfile;
d = a + b + c;
end
As an alternative, you can specify which input file to use:
degree_eq.m:
function d = degree_eq(inputFilename)
eval(inputFilename);
d = a + b + c;
end
and call it as follows:
degree_eq('inputfile');
Related
my matlab script read several wav files contained in a folder.
Each read signal is saved in cell "mat" and each signal is saved in array. For example,
I have 3 wav files, I read these files and these signals are saved in arrays "a,b and c".
I want apply another function that has as input each signal (a, b and c) and the name of corresponding
file.
dirMask = '\myfolder\*.wav';
fileRoot = fileparts(dirMask);
Files=dir(dirMask);
N = natsortfiles({Files.name});
C = cell(size(N));
D = cell(size(N));
for k = 1:numel(N)
str =fullfile(fileRoot, Files(k).name);
[C{k},D{k}] = audioread(str);
mat = [C(:)];
fs = [D(:)];
a=mat{1};
b=mat{2};
c=mat{3};
myfunction(a,Files(1).name);
myfunction(b,Files(2).name);
myfunction(c,Files(3).name);
end
My script doesn't work because myfunction considers only the last Wav file contained in the folder, although
arrays a, b and c cointain the three different signal.
If I read only one wav file, the script works well. What's wrong in the for loop?
Like Cris noticed, you have some issues with how you structured your for loop. You are trying to use 'b', and 'c' before they are even given any data (in the second and third times through the loop). Assuming that you have a reason for structuring your program the way you do (I would rewrite the loop so that you do not use 'a','b', or 'c'. And just send 'myfunction' the appropriate index of 'mat') The following should work:
dirMask = '\myfolder\*.wav';
fileRoot = fileparts(dirMask);
Files=dir(dirMask);
N = natsortfiles({Files.name});
C = cell(size(N));
D = cell(size(N));
a = {};
b = {};
c = {};
for k = 1:numel(N)
str =fullfile(fileRoot, Files(k).name);
[C{k},D{k}] = audioread(str);
mat = [C(:)];
fs = [D(:)];
a=mat{1};
b=mat{2};
c=mat{3};
end
myfunction(a,Files(1).name);
myfunction(b,Files(2).name);
myfunction(c,Files(3).name);
EDIT
I wanted to take a moment to clarify what I meant by saying that I would not use the a, b, or c variables. Please note that I could be missing something in what you were asking so I might be explaining things you already know.
In a certain scenarios like this it is possible to articulate exactly how many variables you will be using. In your case, you know that you have exactly 3 audio files that you are going to process. So, variables a, b, and c can come out. Great, but what if you have to throw another audio file in? Now you need to go back in and add a 'd' variable and another call to 'myfunction'. There is a better way, that not only reduces complexity but also extends functionality to the program. See the following code:
%same as your code
dirMask = '\myfolder\*.wav';
fileRoot = fileparts(dirMask);
Files = dir(dirMask);
%slight variable name change, k->idx, slightly more meaningful.
%also removed N, simplifying things a little.
for idx = 1:numel(Files)
%meaningful variable name change str -> filepath.
filepath = fullfile(fileRoot, Files(idx).name);
%It was unclear if you were actually using the Fs component returned
%from the 'audioread' call. I wanted to make sure that we kept access
%to that data. Note that we have removed 'mat' and 'fs'. We can hold
%all of that data inside one variable, 'audio', which simplifies the
%program.
[audio{idx}.('data'), audio{idx}.('rate')] = audioread(filepath);
%this function call sends exactly the same data that your version did
%but note that we have to unpack it a little by adding the .('data').
myfunction(audio{idx}.('data'), Files(idx).name);
end
I have a segment of code where a composition of nested loops needs to be run at various times; however, each time the operations within the nested loops are different. Is there a way to make the outer portion (loop composition) somehow a functional piece, so that the internal operations are variable. For example, below, two code blocks are shown which both use the same loop introduction, but have different purposes. According to the principle of DRY, how can I improve this, so as not to need to repeat myself each time a similar loop needs to be used?
% BLOCK 1
for a = 0:max(aVec)
for p = find(aVec'==a)
iDval = iDauVec{p};
switch numel(iDval)
case 2
r = rEqVec(iDval);
qVec(iDval(1)) = qVec(p) * (r(2)^0.5 / (r(1)^0.5 + r(2)^0.5));
qVec(iDval(2)) = qVec(p) - qVec(iDval(1));
case 1
qVec(iDval) = qVec(p);
end
end
end
% BLOCK 2
for gen = 0:max(genVec)-1
for p = find(genVec'==gen)
iDval = iDauVec{p};
QinitVec(iDval) = QinitVec(p)/numel(iDval);
end
end
You can write your loop structure as a function, which takes a function handle as one of its inputs. Within the loop structure, you can call this function to carry out your operation.
It looks as if the code inside the loop needs the values of p and iDval, and needs to assign to different elements of a vector variable in the workspace. In that case a suitable function definition might be something like this:
function vec = applyFunctionInLoop(aVec, vec, iDauVec, funcToApply)
for a = 0:max(aVec)
for p = find(aVec'==a)
iDval = iDauVec{p};
vec = funcToApply(vec, iDval, p);
end
end
end
You would need to put the code for each different operation you want to carry out in this way into a function with suitable input and output arguments:
function qvec = myFunc1(qVec, iDval, p)
switch numel(iDval)
case 2
r = rEqVec(iDval); % see note
qVec(iDval(1)) = qVec(p) * (r(2)^0.5 / (r(1)^0.5 + r(2)^0.5));
qVec(iDval(2)) = qVec(p) - qVec(iDval(1));
case 1
qVec(iDval) = qVec(p);
end
end
function v = myFunc2(v, ix, q)
v(ix) = v(q)/numel(ix);
end
Now you can use your loop structure to apply each function:
qvec = applyFunctionInLoop(aVec, qVec, iDauVec, myFunc1);
QinitVec = applyFunctionInLoop(aVec, QinitVec, iDauVec, myFunc2);
and so on.
In most of the answer I've kept to the same variable names you used in your question, but in the definition of myFunc2 I've changed the names to emphasise that these variables are local to the function definition - the function is not operating on the variables you passed in to it, but on the values of those variables, which is why we have to pass the final value of the vector out again.
Note that if you want to use the values of other variables in your functions, such as rEqVec in myFunc1, you need to think about whether those variables will be available in the function's workspace. I recommend reading these help pages on the Mathworks site:
Share Data Between Workspaces
Dynamic Function Creation with Anonymous and Nested Functions
I'm using some user generated functions in MatLab. It'll be quicker if I don't post my actual code here so I'll summarize.
I have two functions. Each of them exist in their own files saved under their proper names. They can be called and work correctly. Lets say function1 is:
function [Output1] function1=(a,b)
Output1=a+b
end
function [Output2] function2=(a,Output1)
Output2=a+Output1
end
new script file
a=2;
b=3;
function1(a,b);
function2(a,Output1);
This doesn't work, because function1 isn't posting Output1 into the workspace. How do I make it do that?
Check this tutorial. This is how you are supposed to write a function.
function Output1 = function1(a, b)
Output1 = a + b;
end
Then your second function will get the input like this.
function Output2 = function2(a, Output1)
Output2 = a + Output1;
end
Of course you need to store answers of functions into variables to have them stored in the workspace.
aa=2;
bb=3;
Output11 = function1(aa,bb);
Output22 = function2(aa,Output11);
If you don't use Output11 and Output22, functions will store their result into ans variable in the workspace. And obviously, apart from the fact that you cannot pass the variable to the second function as Output1, second function will overwrite the ans.
The given task is to call a function from within another function, where both functions are handling matrices.
Now lets call this function 1 which is in its own file:
A = (1/dot(v,v))*(Ps'*Ps);
Function 1 is called with the command:
bpt = matok(P);
Now in another file in the same folder where function 1 is located (matok.m) we make another file containing function 2 that calls function 1:
bpt = matok(P);
What I wish B to do technically, is to return the result of the following (where D is a diagonal matrix):
IGNORE THIS LINE: B = (1/dot(v,v))*(Ps'*inv(D)*Ps*inv(D);
EDIT: this is the correct B = (1/dot(v,v))*(Ps*inv(D))'*Ps*inv(D);
But B should not "re-code" what has allready been written in function 1, the challenge/task is to call function 1 within function 2, and within function 2 we use the output of function 1 to end up with the result that B gives us. Also cause in the matrix world, AB is not equal to BA, then I can't simply multiply with inv(D) twice in the end. Now since Im not allowed to write B as is shown above, I was thinking of replacing (without altering function 1, doing the manipulation within function 2):
(Ps'*Ps)
with
(Ps'*inv(D)*Ps*inv(D)
which in some way I imagine should be possible, but since Im new to Matlab have no idea how to do or where even to start. Any ideas on how to achieve the desired result?
A small detail I missed:
The transpose shouldn't be of Ps in this:
B = (1/dot(v,v))*(Ps'*inv(D))*Ps*inv(D);
But rather the transpose of Ps and inv(D):
B = (1/dot(v,v))*(Ps*inv(D))'*Ps*inv(D);
I found this solution, but it might not be as compressed as it could've been and it seems a bit unelegant in my eyes, maybe there is an even shorter way?:
C = pinv(Ps') * A
E = (Ps*inv(D))' * C
Since (A*B)' = B'*A', you probably just need to call
matok(inv(D) * Ps)
I am trying to allow a function to have access to the base workspace using the evalin function, but I am having trouble. Here is a simple example:
My main code:
A = 1;
B = 2
evalin('base','[ C ] = FUN(B)');
C
My Function:
function [C ] = FUN( B )
C = A + B;
end
My error:
Undefined function or variable 'A'.
Error in FUN (line 4)
C = A + B;
Error in Test (line 4)
evalin('base','[ C ] = FUN(B)');
So, the function is not being evaluated in the base workspace because it does not know what the value of A is.
Can anyone suggest something? I have a lot of variables that I need to access in several functions and I don't want to pass them and I don't want to use global variables.
Thanks!
From the evalin documentation,
evalin(ws, expression) executes expression, a string containing any valid MATLAB® expression, in the context of the workspace ws. ws can have a value of 'base' or 'caller' to denote the MATLAB base workspace or the workspace of the caller function.
So the line of code
evalin('base','[ C ] = FUN(B)');
evaluates only the line of code
[ C ] = FUN(B)
in the context of the base workspace. It does not evaluate the body of the function within the context of the base workspace. So the error that you are observing makes sense.
Is there a particular reason why you don't want to pass the variables in to the function? Why do you have several variables in the base (?) workspace, or do you just have several variables within a main function?
If the latter, you could use nested functions to have access to the variables declared in the caller (function) workspace. For example, suppose you have a main function like
function main()
A = 1;
B = 2;
C = FUN();
function [C] = FUN()
C = A + B;
end
end
The function FUN has access to both A and B and so you don't have to pass in any arguments.
An alternative to passing in several different inputs, is to just pass in a structure that has different fields that your function can access at will. Using the above example, we could do the following
function main()
A = 1;
B = 2;
data.A = A;
data.B = B;
C = FUN(data);
end
function [C] = FUN(data)
C = data.A + data.B;
end
In this case, the function FUN can be a function within its own file or declared after main. Again, we only pass in one argument that has all the data that the function needed.
Actually Evalin function is used to take data from base workspace:
Syntax is :
evalin('base','variable')
Evalin function is used in the function .
For example see the below function
function [out1 out2 out3]=main_fun(in1,in2)
out1=in1+in2;
out2=in1-in2;
in3=evalin('base','in3');
in4=evalin('base','in4');
out3=in3+in4;
end
Here out3 value will have the sum of in3 and in4 from workspace.
out1 and out2 will have the sum and difference of in1 and in2 from current function workspace.