# Joseph Cheng

Systems Engineer for Electro-Optical Systems

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**Content Feed**

How to find intersection between one line and its perpendicular passing by another point

you can follow the computation found here: https://diego.assencio.com/?index=ec3d5dfdfc0b6a0d147a656f0af332bd

4 months ago | 0

Know the number of row within a structure (struct)

so you can use the function find() and contains(). in this example i am just searching the name entry but it should work with y...

5 months ago | 0

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How do I restore default display, with editor and command line?

https://www.mathworks.com/matlabcentral/answers/182333-if-my-editor-window-became-undocked-how-do-i-dock-it-again-picture-inside...

5 months ago | 0

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Extracting data from another column based on row conditions

So if we create a simple example C = [-6:6]';E=C;E(1:5)=nan;B=2*C;Table = table(C,E,B) Table.X(Table.C > 0 & isnan(Table.E)) =...

5 months ago | 0

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Create different outline colors for different times

you can generate a color scale by using the different types of colors like hsv, jet, bone, gray, etc. then depending on the tim...

1 year ago | 1

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Change scale of x-axis on plot

check this answers post here: https://www.mathworks.com/matlabcentral/answers/398481-how-do-i-remove-scientific-notation-from-x...

1 year ago | 1

App Designer: How to plot graph from own function into UIAxess?

if you look at the plot() function or any other display/plotting tools like imagesc(), image(), imshow(), etc... the first entry...

1 year ago | 0

I got Error using vertcat Dimensions of arrays being concatenated are not consistent. Error in Code_tubes (line 22) C = [q(1); q(2); q(3);

a quick scan shows it at the last row of C with q(6) - teta2_o - w2*t]; where everything up to that looks to b...

1 year ago | 0

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How do I pass coefficients to function handle as an array or list?

i think you just answered yourself in your question y = @(y0,a,b,NN) y0 + a*x(NN) + b*x(NN).^2; %simulate parabolic data yDIF...

2 years ago | 1

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Issue in plotting binary image boundaries with real axis values

so you'll need to find the conversion between pixel to linear xy (mm). sort of the mm/px scale factor + offset to 0; from th...

2 years ago | 0

how can i automatically crop this image? if it is possible.

well, you can find the corner squares by doing the following: img = (imread('https://www.mathworks.com/matlabcentral/answers/up...

2 years ago | 0

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Create variable with name from other variable string

While it is not adviseable to have variables created in this way maybe you have a good reason to but still un-adviseable but her...

2 years ago | 1

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How to find end of time series in plot

to go with your example of pos where pos = [0.11, 0.12, 0.12, 0.12, 0.12 0.12, 0.14, 0.14, 0.11, 0.16, 0.13, 0.13, 0.13, 0.13]...

2 years ago | 0

remove empty rows of a cell

you can use the function cellfun() in conjunction with isempty: clear K %generate dummy K for Cind = 1:2 for Rind = 1:4 ...

2 years ago | 0

Issues in For loop

if we break down your for loop: for i=1:38976; %this if statement will be done if j==120 %an okay statement here b...

2 years ago | 1

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How to find the two minimum values ?

well to remedy this you shouldn't "delete" the entry of the min point but stick in a large value or Nan and use nanmin(). by de...

2 years ago | 0

3d to 2d matrix

take a look at the function squeeze() for ind = 1:3 val(1,1,ind)=-ind; end disp(val) u2 = squeeze(val); disp(u2)

2 years ago | 1

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How to get data points within current camera view?

So... if i'm not mistaken pan in matlab moves the axes limits of the plot and not panning/translating the camera, similarly zoom...

2 years ago | 0

Looking for a way faster than find?

without doing some testing to actually test if its faster you can use the found 1's in a to only select a list of indexes A = ...

2 years ago | 0

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Incorrect datatip location on interpolated data

so you can see what is happening if you plot it as just markers in this animated example: figure; hold on; hPlot = plot(1:10, ...

2 years ago | 0

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Taking average of pixel values across multiple frames

couldn't you just put it into a non cell matrix of 5504 x8256 x 3 then use mean(data,3) to take the mean in the 3rd dimension? o...

2 years ago | 1

Why am I getting an invalid file identifier error when using "parfor" but the same function works fine (albeit slow) with "for"?

From the looks of it you've opened a file then trying to use parfor to grab items out of the opened file. However thats where t...

2 years ago | 0

How to get rid of blank space in a heatmap panel of 3 figures?

have you looked at the functions axis equal or axis square those might be applicable to you and not have to only use top h...

2 years ago | 0

How read in comment style to skip the header of a text file?

you can quickly scan the file(s) for the number of header lines like file= 'Graphite_Node_test.txt'; fid = fopen('Graphite_Nod...

2 years ago | 0

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Contour is plotting my data in reflected order?

From a quick test you might not be asigning the x and y values when performing your contour() function. by doing so matlab will...

2 years ago | 0

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Create a matrix with elements clockwise

While probably not the most efficient way you can fill in edges like i've done here: clc;clear all x = zeros(5,8); %generate m...

2 years ago | 1

Update a for loop with if statements

Without running your code i think you can create a sign variable of (-1)^(0 or 1) which switches between 0 or 1 depending on whe...

2 years ago | 0

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Represent array in percentage

you would take your array, subtract the minimum, then divide by the resulting maximum x 100 x = [2.4:.4:4.2]; x = x-min(x); ...

2 years ago | 1

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How to make the length/dimension of 6 different 3D vectors the same?

probably the easiest way is to fill a zero array created to be the same max size then populate the indexes with the values: var...

2 years ago | 1

| accepted