I need to find the "null vector" of the matrix in LabVIEW. But I couldn't find the related block.
For example in MatLab, for the Matrix A we can simply find the null vector with the command: null(A); But in LabVIEW I can't do this till now.
Could someone help me?
One easy way to do this is to use the MathScript node, which allows for many Matlab commands to be used in LabVIEW. Here's an example:
If you don't want to use the MathScript node, then you can get the result from the "Matrix V" output of "SVD decomposition" as shown in the second part of the code.
Related
I'm trying to implement an algorithm which has been described in a paper. It deals with accelerometer data which has to be filtered and differentiated. My input is a vector (1 column, multiple rows).
As described here
The vector has to differentiated using a Gaussian CWT with the MatLab function cwt. Scale has to be 'scale10' and wavelet 'gaus1'.
When I try to implement the instructions in MatLab, I type the following:
dudx=cwt(vector,'scale10','gaus1');
This is the error I get:
Undefined function 'sqrt' for input arguments of type 'char'.
Error in cwt (line 278)
coefs(ind,:) = -sqrt(a)*wkeep1(diff(wconv1(ySIG,f)),lenSIG);
As it should actually work with the input, I've really no idea what I could change. I also went through the mathworks pages from cwt and wavefun but without any solution.
I've never before used a CWT, therefore I thought that I may misunderstood something and applied the instructions wrong. Can anyone help me out on this?
You're not using the function right. The second parameter is a vector of scales where each number is the desired scale you want. scale10 doesn't mean anything. Do you want the 10th scale?
Do this:
dudx=cwt(vector,10,'gaus1');
Please read the documentation here: http://www.mathworks.com/help/wavelet/ref/cwt.html
In MATLAB R2014b there is a new function, pca(), that performs PCA that can handle missing data. In the documentation it says that it performs pca with the "alternating least squares" algorithm in order to estimate the missing values.
I would like to know if there are any practical references in how to apply PCA with this algorithm without the use of the function, or if there is a good reference on als. The reason is, there is no such function in Octave that can handle missing data and so I would like to code it myself.
Thanks for all your help. I went through the references and was able to find their matlab code on the als algorithm from two of the references. For anybody wondering, the source code can be found in these two links:
1) http://research.ics.aalto.fi/bayes/software/index.shtml
2) https://www.cs.nyu.edu/~roweis/code.html
pow=fsolve(#eqns,pop);
This is the code I am using to solve a 2x2 non-linear system of equations, defined in the function eqns.m.
pop is a 2x1 initialisation vector pretty close to the solution. When I run it, the output says
No solution found.fsolve stopped because the relative size of the current step is less than the default value of the step size tolerance squared, but the vector of function values is not near zero as measured by the default value of the function tolerance.<stopping criteria details>
Any way out? I tried moving the initial point further away from the solution intentionally, still it is not working. How do I set the tolerance or some other parameter? Some posts gave me the impression that supplying the jacobian to matlab can be helpful, but how do I do that? Please note that I need the solution in the form of a code which I can put in a function file to be called repeatedly. I believe the interactive optimtool toolbox would not help here. Any help please?
Also from the documentation, the fsolve can employ three different algorithms. Is any of them more helpful than the others for certain problem structures? Where can I get a comparative study of them, suitable for some non-expert in optimisation?
I've been given a set of about 20k data points. I managed to import the data into Matlab and did the following :
importdata;
fft(importdata);
and it returns :
Undefined function 'fft' for input arguments of type 'cell'
Now, I understand that I need more than this to get it working.
Can someone please tell me any more parameters I need for the fft and how to implement it?
Edit: These datapoints are timestamps of when something is detected in a machine,
I'm trying to find if there is a period of the detection occuring.
Look at the documentation for the correct way to use importdata and fft. Both have examples to get you started.
First you need to assign the output of importdata to a matrix, then do any data manipulation you need to get it in a form to be used by fft. Finally, use fft with the correct parameters and compute the correct frequency vector as per the example (obviously, adapted to your data)
My teacher wants us to find the basis of the null space of a function in MATLAB. This is the exact question.
Use the MATLAB function rref and the function lead above to write a MATLAB
function N=nullbase(A) which computes a matrix N whose columns form a basis
for the nullspace of A. Your file nullbase.m should not use the MATLAB functions
rank or null.
Please someone help me, thank you.
What you're looking for is the SVD (singular value decomposition). Because this sounds like a homework problem, I won't give away the whole answer, but this hint should help. MATLAB has an SVD function: http://www.mathworks.com/help/techdoc/ref/svd.html