# Steve Eddins

### MathWorks

MATLAB user since 1987. MathWorker since 1993. Amateur French horn player. MATLAB design and development, image processing algorithms.

Image processing blog: https://blogs.mathworks.com/steve/

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**Content Feed**

Can a MATLAB function edit the input?

You'll need your class to subclass handle. See the documentation page "Implementing Linked Lists with Classes" for details.

28 days ago | 0

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Matlab working very slow on my m1 MacBook Pro

See this answer and follow it for updates related to this problem.

2 months ago | 2

Shouldn't bwconvhull() be idempotent?

Hi Matt, At a general level - and speaking from too much personal experience - expectations about geometrical operations such a...

3 months ago | 2

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Issue in plotting binary image boundaries with real axis values

The function bwboundaries returns boundary values in pixel coordinates. You'll need to scale those to world coordinates yourself...

3 months ago | 0

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How to change boundary width in Active Contour Method?

Call visboundaries with an output argument. That output argument will be an hggroup object containing two lines. You can then ma...

3 months ago | 0

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Published

Use imbinarize to Threshold Gray-Scale Images

Today, I want to convince you to use imbinarize instead of im2bw.Background: I recently saw some data suggesting that many...

3 months ago

Published

NaN Sightings

Some of us at MathWorks like to share our "NaN sightings." Here is an example to show what I mean. This is a screenshot of...

4 months ago

Published

How to Use a Custom Interpolation Kernel with imresize

Recently, I was talking with MathWorks writer Jessica Bernier about the reference page for the imresize function. Jessica...

4 months ago

Published

How to Run Blog Post Code in Your Browser

I have published more than 560 blog posts here since 2006, and I estimate that about 98% of them started out as MATLAB...

5 months ago

Published

Plotting a* and b* colors

Today's blog post comes from planning one topic, but then taking a sharp left turn and doing something else completely. I...

5 months ago

Having graycomatrix rescaling problem

Here is the doc for the NumLevels parameter: Number of gray levels, specified as an integer. For example, if NumLevels is 8, gr...

5 months ago | 0

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How to find the center position under the saturation spot signal

Try converting the image to binary using imbinarize and then using regionprops to compute the centroid. rgb = imread('image.bmp...

5 months ago | 0

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How to bold x axis labels

Try setting the TickLabelsInterpreter property to 'tex', like this: plot(1:10) ax = gca; ax.XAxis.TickLabelInterpreter = 'tex...

6 months ago | 0

three difference vectors and plots

I have copy-pasted your code below, exactly as entered in your question. It runs and produces the plot with no error. I suggest ...

6 months ago | 2

Problem with datetime and daily values

Use a timetable and the retime function. >> T = readtable("data.xlsx"); >> head(T) ans = 8×5 table Date ...

6 months ago | 0

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What is the best way to count the occurrences of two table columns together?

In my previous answer, I forgot that grpstats is in the Statistics and Machine Learning Toolbox. Here is an answer using groupsu...

6 months ago | 1

What is the best way to count the occurrences of two table columns together?

I think grpstats will do what you want: >> grpstats(T,["A" "B"]) ans = 4×3 table A B Grou...

6 months ago | 0

Find peaks not working on my data set

I suspect the issue is with the x-coordinates that you are using to plot the peaks. You are plotting the peaks against the indic...

6 months ago | 1

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Assign values in a matrix

One idea is to use a timetable and the retime function. Suppose I have the following matrix for a 4-minute charge and a 3-minute...

6 months ago | 0

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Code is showing Undefined function 'pixelHull' for input arguments of type 'double'.

I wrote a function called pixelHull as part of my 16-Mar-2018 blog post. You can find the function listing near the bottom of th...

7 months ago | 0

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Published

FFT Spectral Leakage

A MATLAB user recently contacted MathWorks tech support to ask why the output of fft did not meet their expectations, and...

7 months ago

Binarize image for specific colour

Use the Color Thresholder app to generate the code needed to do this segmentation. See my 14-Oct-2019 and 25-Apr-2014 blog posts...

7 months ago | 0

Plotting signal of a region of interest

A possible explanation is that you have a variable called "size" or "mean" in your workspace. For example, if you have a variabl...

7 months ago | 0

How to apply a threshold value to the cell array

I think writing a for-loop would be most straightforward way to go. Something like this: for k = 1:numel(C) C_k = C{k}; ...

7 months ago | 1

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How to change the font of a pie chart?

The text labels created by the pie function are not controlled by the font properties of the containing axes object. They are in...

8 months ago | 2

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superimpose matrices (n,n,m) to (n,n,1)

Here are some options. Compute and plot the maximum value at each pixel: imagesc(max(a100,[],3)) Compute and plot the minimum...

8 months ago | 0

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Image conversion from uint16 to uint8 mismatch

im2uint8 is using a scale factor of (255/65535), not 1/256. Note that scaling the maximum of the uint16 range, 65535, by 1/256 ...

8 months ago | 1

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How do I map array values on a logical array

Use logical indexing. C = zeros(size(B)); C(logical(B)) = A

8 months ago | 1

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Create a 7x7 convolution kernel which has an equivalent effect to three passes with a 3x3 mean filter.

Convolution is associative: So, your 7x7 convolution kernel would be the convolution of the mean filters: Use the 'full' o...

8 months ago | 0

pgm image lossless compression

Write the image to a PNG file. The PNG format uses lossless compression. imwrite(A,'myfile.png') Read it back in using imread....

8 months ago | 0