# Chris Turnes

### MathWorks

I'm an electrical engineer by education.

Professional Interests: signal processing, image processing, linear algebra.

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**Content Feed**

Need (Basic) Help Using nufftn for Complex-Valued Scalar Function of 2 Variables

If Is and Js are the coordinates of your non-uniform data, and both Is and Js have N = numel(Vs) elements, then probably what yo...

1 month ago | 0

| accepted

Can we have a very simple and clear comparison example on the functions fft and nufft works?

The key thing to remember is that since nufft takes the sample points and frequency points as arguments, you have to remember ho...

3 months ago | 1

| accepted

nufft and aliasing errors

What you are observing here is the effects of non-uniform sampling; the further you get from uniform sampling, the less you can ...

10 months ago | 0

How to use nufft or nufftn to compute NonUniformFFT of an image with missing (not sampled) pixels?

I'm not sure what format your data is in; however, for the purposes of showing how you might do this, suppose you had a list of ...

10 months ago | 0

Nufftn yields only zeros for nonuniform grid. Bug?

Yes, this appears to be a bug. Please open a case with technical support.

1 year ago | 0

| accepted

when smoothing data with gaussian how to define sd and mean

The 'gaussian' method for smoothdata uses a fixed (but window-dependent) standard deviation, and mean of zero. If you want to s...

2 years ago | 1

| accepted

Moving Average of Matrix over 10 min interval

The error message could be clearer about the problem you're having, but you're getting the message because you've misspelled "Sa...

2 years ago | 0

find local maxima around a point

If you can provide a MAT file with the data, it would be helpful in answering the question more concretely. You should be able ...

2 years ago | 0

Cut a signal into heart cycle pieces

I don't have your data, but using something that looks roughly similar (attached), here's an approach. Furthering John's commen...

3 years ago | 1

| accepted

How do I identify subsets of data and divide the data into the subsets

Mark's answer is a great way of doing this. In addition, you might consider looking at the ischange function: % Look for at mo...

3 years ago | 0

How does "smoothdata" function using "gaussian" method define the standard deviation for different window size?

The standard deviation of the Gaussian for |smoothdata| is fixed to be 1/5th of the total window width, so there is a direct lin...

3 years ago | 3

| accepted

How to make a softer plot using a moving average every ''x'' skips?

It sounds like what you might want to do is put your data into a <https://www.mathworks.com/help/matlab/ref/timetable.html |time...

3 years ago | 0

Using smoothdata on tallaray that contains time

|smoothdata| does not support tall timetables, and similarly does not support the |'SamplePoints'| Name-Value pair for tall inpu...

4 years ago | 0

how to find and mark the value of local minimums in a graph of multiple data ?

If you have access to R2017b, you might also consider checking out the <https://www.mathworks.com/help/matlab/ref/islocalmin.htm...

4 years ago | 0

Find sudden jumps in signal

If you have access to R2017b, try taking a look at the <https://www.mathworks.com/help/matlab/ref/ischange.html |ischange| funct...

4 years ago | 0

Data segmentation for Accelerometer time series data

For the segmentation, if you have R2017b, <https://www.mathworks.com/help/matlab/ref/ischange.html the new |ischange| function> ...

4 years ago | 0

How to write a circulant matrix , where the elements are matrices? Thanks!

Supposing the matrices you want to use in a circulant pattern are stored as a |M| x |N| x |K| array (where |M| x |N| is the size...

4 years ago | 0

Sorting the complex array elements with imaginary part along with it.

If you have a recent version of MATLAB, try checking out the <https://www.mathworks.com/help/matlab/ref/sort.html#namevaluepaira...

4 years ago | 2

Efficient moving average of scattered data

If you can upgrade to R2017a, this functionality can now be achieved through the 'SamplePoints' name-value pair in the moving st...

5 years ago | 1

Delete rows with NaN records

Not that this question needed another answer, but, you can also check out the <http://www.mathworks.com/help/matlab/ref/rmmissin...

5 years ago | 2

How to replace a NaN element with an preceeding element in a matrix using logical indexing?

As far as replacing with the previous non-NaN element, you could check out the <http://www.mathworks.com/help/matlab/ref/fillmis...

5 years ago | 0

How to use "movsum()" with panel data in a table using loop mechanisms?

I think you just want to use |sum| here, and not |movsum|, since you're summing over different columns each time. Regardless, t...

5 years ago | 1

| accepted

How to calculate Sums in a Panel Data framework using "For Loops"

To get the moving sum of the previous 12 elements, and marking all windows NaN where you don't have 11 previous points, you can ...

5 years ago | 0

| accepted

Convolution of many vectors

You can use a fun trick here. Each of these polynomials is a quadratic, so you can find their roots easily enough: F = F(:...

5 years ago | 0

How to exclude the center/current number when performing movmax?

There's no direct way to exclude the current point in a given window with the moving statistics functions. However, since you w...

5 years ago | 1

| accepted

Help on calculating cumulative moving average

If you're trying to do a cumulative moving mean, where each time you move to the next element it is the mean of that element and...

5 years ago | 2

mean value of a group of data with NaNs

You can also just use the 'omitnan' option in "mean": A = [1 0 0 1 NaN 1 NaN 0]; M = mean(A,'omitnan') M = 0.5...

5 years ago | 2

How to convert the mean value of an integer matrix to a double

Are regionA and regionB allocated as integers? It seems likely he final assignment that is casting them back to integers. Sinc...

5 years ago | 0

| accepted

How to limit rounding in matrix division

Your last sentence has the answer: your data type is uint8. Dividing a uint8 by a uint8 is going to give you another integer, s...

6 years ago | 0

How to interpolate for given inputs in a n*m matrix

If I understand your question correctly, it sounds like <http://www.mathworks.com/help/matlab/ref/griddedinterpolant-class.html ...

6 years ago | 0

| accepted