I'm creating my own function in Matlab and I want to be able to display it like so below, when I type 'lookfor'.
>> lookfor mean
mean - Average or mean value.
msfun_metronomean - METRONOMANIMATION S-function for making metronomean animation.
mameannorm - normalizes microarray data by dividing by global mean.
distfcm - Distance measure in fuzzy c-mean clustering.
fcm - Data set clustering using fuzzy c-means clustering.
initfcm - Generate initial fuzzy partition matrix for fuzzy c-means clustering.
stepfcm - One step in fuzzy c-mean clustering.
I've heard it can be done by typing a line directly below the declaration of the function as can be seen below:
function [outputArgs] = TestFunction(inputArgs)
%TESTFUNCTION Summary of this function goes here
However I've tried this and it still doesn't appear in the list of lookups?
Any help would be greatly appreciated.
Thanks in advance!
It is not clear what you have done. For a function like
function [outputArgs] = TestFunction(inputArgs)
%TESTFUNCTION Summary of this function goes here
I would not expect lookfor mean to find it. The documentation of lookfor is pretty clear
lookfor topic searches for the string topic in the first comment line
(the H1 line) of the help text in all MATLAB® program files found on
the search path. For all files in which a match occurs, lookfor
displays the H1 line.
lookfor topic -all searches the entire first comment block of a MATLAB
program file looking for topic.
If you want lookfor mean to find your function you need to have the H1 line include the word "mean"
function [outputArgs] = TestFunction(inputArgs)
%TESTFUNCTION Summary of this function goes here (mean)
Then lookfor mean works fine.
I'm not sure exactly what I changed but it now works now. I'm sure it was something to do with the file path that the project was stored in. Thanks for your help though guys.
Related
I have the following function that I wish to solve using fzero:
f = lambda* exp(lambda^2)* erfc(lambda) - frac {C (T_m - T_i)}/{L_f*sqrt(pi)}
Here, C, T_m, T_i, and L_f are all input by the user.
On trying to solve using fzero, MATLAB gives the following error.
Undefined function or variable 'X'.
(where X are the variables stated above)
This error is understandable. But is there a way around it? How do I solve this?
This is answered to the best of my understanding after reading your question as it's not really clear what you are exactly trying and what you want exactly.
Posting the exact lines of code helps a big deal in understanding(as clean as possible, remove clutter). If then the output that matlab gives is added it becomes a whole lot easier to make sure we answer your question properly and it allows us to try it out. Usually it's a good idea to give some example values for data that is to be entered by the user anyway.
First of to make it a function it either needs a handle.
Or if you have it saved it as a matlab file you generally do not want other inputs in your m file then the variable.
So,
function [out]=yourfun(in)
constants=your values; %you can set a input or inputdlg to get a value from the user
out= something something, your lambda thingy probably; %this is the equation/function you're solving for
end
Now since that is not all that convenient I suggest the following
%declare or get your constants here, above the function makes it easier
syms lambda
f = lambda* exp(lambda^2)* erfc(lambda) - frac {C (T_m - T_i)}/{L_f*sqrt(pi)};
hf=matlabFunction(f); %this way matlab automatically converts it to a function handle, alternatively put #(lambda) in front
fzero(hf,x0)
Also this matlab page might help you as well ;)
Hi, I am trying to write a function as per the question. I have tried to create four sub-matrices which are the reverse of each other and then multiply to give the products demanded by the question. My attempt:
function T = custom_blocksT(n,m)
T(1:end,end-1:1);
T(1:end,end:-1:1)*2;
T(1:end,end:-1:1)*3;
T(1:end,end:-1:1)*4;
What I'm unsure of is
(i) What do the the indivual sub-matrices(T(1:end,end-1:1);)need to be equal to? I was thinking of(1:3)?
(ii) I tried to create a generic sub-matrix which can take any size matrix input using end was this correct or can't you do that? I keep getting this error
Undefined function or variable 'T'.
Error in custom_blocksT (line 2)
T(1:end,end-1:1);
I have searched the Matlab documentation and stacked overflow, but the problem is I'm not quite sure what I'm supposed to be looking for in terms of solving this question.
If someone could help me I would be very thankfull.
There are many problems with your function:
function T = custom_blocksT(n,m)
T(1:end,end-1:1);
T(1:end,end:-1:1)*2;
T(1:end,end:-1:1)*3;
T(1:end,end:-1:1)*4;
end
This is an extremely basic question, I highly recommend you find and work through some very basic MATLAB tutorials before continuing, even before reading this answer to be honest.
That said here is what you should have done and a bit of what you did wrong:
First, you are getting the error that T dos not exist because it doesn't. The only variables that exist in your function are those that you create in the function or those that are passed in as parameters. You should have passed in T as a parameter, but instead you passed in n and m which you don't use.
In the question, they call the function using the example:
custom_blocks([1:3;3:-1:1])
So you can see that they are only passing in one variable, your function takes two and that's already a problem. The one variable is the matrix, not it's dimensions. And the matrix they are passing in is [1:3;3:-1:1] which if you type in the command line you will see gives you
[1 2 3
3 2 1]
So for your first line to take in one argument which is that matrix it should rather read
function TOut = custom_blocks(TIn)
Now what they are asking you to do is create a matrix, TOut, which is just different multiples of TIn concatenated.
What you've done with say TIn(1:end,end-1:1)*2; is just ask MATLAB to multiple TIn by 2 (that's the only correct bit) but then do nothing with it. Furthermore, indexing the rows by 1:end will do what you want (i.e. request all the rows) but in MATLAB you can actually just use : for that. Indexing the columns by end-1:1 will also call all the columns, but in reverse order. So in effect you are flipping your matrix left-to-right which I'm sure is not what you wanted. So you could have just written TIn(:,:) but since that's just requesting the entire matrix unchanged you could actually just write TIn.
So now to multiply and concatenate (i.e. stick together) you do this
TOut = [TIn, TIn*2; TIn*3, TIn*4]
The [] is like a concatenate operation where , is for horizontal and ; is for vertical concatenation.
Putting it all together:
function TOut = custom_blocks(TIn)
TOut = [TIn, TIn*2; TIn*3, TIn*4];
end
I have a project to transform an image using dwt.
I successfully done it using function dwt2, and now I try to use function dwt3 by changes some code from the function dwt2 (add more subband: 8 subbands). Unfortunately, an error comes out, which said "Too many output arguments".
My question is, what is the right way to write MATLAB code for dwt3? Is it not same as dwt2, just add more subbands?
Just by looking at the official documentation for dwt2 and dwt3, I see that dtw3 has only 1 output variable, whereas dtw2 has 4.
I assume you just replaced the string dtw2 in your code to dwt3, without paying attention to the amount of allowed output variables. So there you go, that's where the error "too many output variables" comes from...
If dwt3 only returns the transformed vector, cut the number of output variables to 1, and I'm sure the error will away:
Y = dwt3(X, 'db2');
Here I transformed X using dwt3 with the Daubechies 2-tap wavelet, and stored the result in Y.
P.S
You need to show more code if you want more productive, helpful answers...
http://www.mathworks.com/help/techdoc/ref/fftshift.html
If you check that link - thats what I want to do in the first picture - swap quadrants of a matrix.
However, I cant seem to think of a good way to do this without having several loops to pull out the relevant sub-matrices.
I need it to work with MxN matrices, where M and N can be any combination of even and odd.
Thanks
The following should work
sz = ceil(size(A)/2)
A = A([sz(1)+1:end, 1:sz(1)], [sz(2)+1:end, 1:sz(2)])
That only works for 2d matrices, but can be easily generalized to the Nd case.
If you enter type fftshift.m at MATLAB's command line, you'll see the source code for MATLAB's implementation of the function (use edit fftshift.m if you want to view it in the editor with syntax highlighting). I'm not posting the code here, as it is copyrighted. However, you can try it on your machine and re-implement the same in C. Its up to you to figure out the license terms etc, if you're into any of that.
I want to plot a piecewise function, but I don't want any gaps to appear
at the junctures, for example:
t=[1:8784];
b=(26.045792 + 13.075558*sin(0.0008531214*t - 2.7773943)).*((heaviside(t-2184))-(heaviside(t-7440)));
plot(b,'r','LineWidth', 1.5);grid on
there should not be any gaps appearing in
the plot between the three intervals , but they do.
I want the graph to be continueous without gaps.
Any suggestions on how to achieve that.
Thanks in advance.
EDIT
Actually, my aim is to find the carrier function colored by yellow in the figure below. I divide the whole interval into 3 intervals: 1-constant 2-sinusoidal 3- constant, then I want to find the overall function from the these three functions
Of course there are "gaps". The composite function is identically zero for all t<2184, and for all t>7440. The relationships can only be non-zero inside of that interval. And you have not chosen a function that is zero at the endpoints, so how can you expect there not to be "gaps"?
What values does your function take on at the endpoints of the interval?
>> t = [2184 7440];
>> (26.045792 + 13.075558*sin(0.0008531214*t - 2.7773943))
ans =
15.689 20.616
So look at the hat function part of this. I'll be lazy and use ezplot.
>> ezplot(#(t) ((heaviside(t-2184))-(heaviside(t-7440))),[0,8784])
Now, combine this, multiplying it by a trig piece, and of course the result is identically zero outside of that domain.
>> ezplot(#(t) (26.045792 + 13.075558*sin(0.0008531214*t - 2.7773943)).*((heaviside(t-2184))-(heaviside(t-7440))),[0,8784])
But if your goal is some sort of continuous function across the two chosen points in the hat function, you need to chose the trig part such that it is zero at those same two points. Mathematics is not spelled mathemagics. Wishing that you get a continuous function will not make it so.
So is your real question how to chose that internal piece (segment) as one such that the final result is continuous? If so, then we need to know why you have chosen the arbitrary constants in there. Surely these numbers, {26.045792, 13.075558, 0.0008531214, 2.7773943} all must have some significance to you. And if they are important, then how can we possibly make the result a continuous function?
Perhaps, and I'm just guessing here, you want some other result out of this, such that the function is not identically zero outside of those bounds. Perhaps you wish to extrapolate as a constant function outside of those points. But to help you, you must help us.