Community Profile # the cyclist

### Alden Scientific

Last seen: Today Active since 2011

Head of Modeling and Statistics at Alden Scientific. Obsessive runner. Professional Interests: Predictive modeling, statistics. (I don't respond to email via author page, but will usually look at a question if you send me a link to it.)

Programming Languages:
Python, R, MATLAB, SQL
Spoken Languages:
English

#### Statistics

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sqrtm vs chol to produce draws the multivariate normal distribution
A common reason for not having a positive semidefinite correlation matrix is when the pairwise correlations are estimated (or ob...

1 hour ago | 1

Truncated answers when querying chatgpt with Matlab
My impression from searching the same topic is that there is an unpublished token limit (which will roughly translate to a chara...

1 day ago | 0

How to extract diagonal elements of multidimensional array ?
rng('default') N = 4; A = rand(N,N,N); A(1:N^2+N+1:end)

2 days ago | 3

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Using histcounts to determine loose data mode
I think that you have a case of the XY problem here. Namely, you are asking about your solution to a particular problem, but I s...

2 days ago | 0

plotting functions over domain
f = @(x,y) (x.^2 + 3*y.^2).*exp(1 - x.^2 - y.^2); % I'm not certain about your notation here x = -1 : 0.05 : 1; y = -1 : 0.0...

3 days ago | 0

I have 2 columns, i want to find the maximum in the second column and then know what value it is next to on the first column
% Pretend data aw = rand(1221,2) + 250; % Max 2nd col in range, with index [maxW,idx] = max(aw(651:1221,2)); % Absorbanc...

3 days ago | 0

Combinations and Matrices?
There just happens to be a very obfuscated way to do this: M = dec2bin(0:2^20-1) - '0'; size(M)

4 days ago | 0

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How does the classification learner app implement k-fold cross validation?
I am most definitely not an expert in this app, but I built a simple model using the default settings, and then exported the fun...

5 days ago | 0

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fit tool with errors in x and y
I am late to seeing this question, but FYI there is a submission to the File Exchange that does linear, univariate Deming regres...

5 days ago | 0

Issues plotting simple bar graph.
The error message is quite clear. Your X values are not unique. Let's look at a simpler example: x = [1 2 2]; y = [3 5 7]; ...

6 days ago | 0

Strategy on how to save data from multiple runs of an experiment where variables changes
There's probably no single best answer here. But if the overall scale of the data is not too large, storing everything in one ta...

7 days ago | 0

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Pie chart with arrows without text coincidence on each other
This is a case where you need to ask yourself, "What is the information I really need to convey to my audience, and what is the ...

7 days ago | 1

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How to transpose every cell in a table?
% If data are in a cell array c = {rand(1,7),rand(1,27)} ctrans = cellfun(@transpose,c,'UniformOutput',false) % If data...

7 days ago | 1

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what is the meaning of this error? how to stop this error?
One reason for getting that error is having text in a line before the function definition. So if your function file looks like t...

7 days ago | 0

How to give variable name to a Mat file?
Your code is looking for a variable named X1. The file X1.mat that you load does not contain a variable named X1, it is just nam...

7 days ago | 0

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Append multiple values in one variable
Assuming the image are all the same size, 512x512, then I would "stack" them in the 3rd dimension, then convert everything to a ...

8 days ago | 0

Use cvpartition to generate a set of random 3 numbers 100 or 1000 times
I don't think cvpartition does what you intend, and I am quite sure that you don't understand its output. Rather than explain cv...

8 days ago | 0

Most efficient way of looking up values in an array.
One simple step that could speed up your code a lot would be to preallocate memory for your output array. Put myIntegers = zero...

8 days ago | 0

matlab some polyfit problem
It is admittedly confusing, and I have fallen into this trap myself. The reason for the difference is described in the documenta...

8 days ago | 0

How to calculate the correlation matrix of two jpg images of the same size?
The result is what I would expect. Imagine this smaller example, with two images of 9 random pixels: rng default N = 3; img...

9 days ago | 0

Finding the predictors of a neural network
Suppose each of your 70 predictors is a binary variable. That means that there are 2^70 possible combinations of predictors. F...

10 days ago | 0

Find column number for every row in matrix
Here is one way: M = [-1 4 1; 1 -1 -1; -5 4 -1]; [r,c] = find(M>0); [~,j] = unique(r); ...

10 days ago | 0

How do I crop a matrix within desired numerical limits?
I am unclear what you mean by "crop" here. I can think of two possibilities: Remove rows of your matrix that have values outsid...

10 days ago | 0

How do I fix "Index in position 2 exceeds array bounds. Index must not exceed 1." as error?
Notice that when you used import data, it came is as a structure. So, you would need to access data.data. data = importdata('C...

13 days ago | 1

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Convert a table in a pdf to a MATLAB cell structure
I can strongly recommend using Tabula to first extract the table from the PDF file. Then use a MATLAB function (e.g. readtable) ...

13 days ago | 0

How do I fix "Index in position 2 exceeds array bounds. Index must not exceed 1." as error?
It would be easier for us to help you debug this if you upload the data. You can use the paper clip icon in the INSERT section o...

13 days ago | 1

What algorithms can perform multiple output regression?
The mvregress function in the Statistics and Machine Learning Toolbox will perform linear regressions with multiple dependent va...

13 days ago | 0

How to I validate a string to ensure it contains a valid Date .
Here is one way: MyStr = '23max2023'; % Invalid string will give an empty array isMyDateFormat = regexp(MyStr, '\d{2}(jan|feb|...

14 days ago | 0