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# Peng Li

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126 total contributions since 2020

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Question

speed up renamecats/categorical multiple columns
I have a huge csv file of about 16GB which over 9k columns. Each column is initially filled with some codes (either integer or s...

15 jours ago | 0 answers | 0

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Extracting and plotting max/min values from timeseries
Better take advantage of table format and splitapply function. tbl = readtable('data.csv'); tbl.day = day(tbl.Date); tbl.h...

15 jours ago | 0

| accepted

What does the ' symbol mean?
transpose. https://www.mathworks.com/help/matlab/ref/transpose.html

15 jours ago | 0

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Question

datastore readsize and buffer chunk
I am working with a single csv file of over 10G size. I'm trying to use mapreduce to perform some analyses. The program works as...

15 jours ago | 1 answer | 0

### 1

How can i get contour plot like this?
https://www.mathworks.com/help/matlab/ref/contourf.html This might be what you need.

15 jours ago | 1

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Can some one please tell me how to find the maximum amplitude frequency of the ecg signal? I have attached below my code. I keep getting maximum frequency at 0 Hz.
try Y = fft(ecgData - mean(ecgData), NFFT); It is expected that the DC contains most of the energy of the signal. You could e...

16 jours ago | 0

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Having trouble with legend
Try this %Line Colors strColor = {'-r','-g','-b'}; %Legend String strLegend = {'nSamples = 5','nSamples = 10','nSamples = 15...

16 jours ago | 0

convert a double matrix in cell within a table
t = table([ones(1, 4); ones(1, 4)*2; ones(1, 4)*3]) t = 3×1 table Var1 ________________ 1...

16 jours ago | 1

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Finding average of a large csv file
why do you need a loop? you said you have ONE cvs file with 1 column and 301 rows? you just need to import the cvs file and do t...

16 jours ago | 0

Indices of the values for which two conditions are true
tbl = table(abbrev(:), firstword(:), number(:)); [gp, outTbl] = findgroups(tbl(:, 1:2)); outTbl.sum = splitapply(@sum, tbl.(3)...

16 jours ago | 0

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Help with Linear Mixed effects model formulas
For statistical questions, the first thing we ask is what the hypothesis is. From your equation, I guess you'd like to examine ...

16 jours ago | 0

How can i export data from an 'edit text box' in app designer to an excel file?
I assume that you have properties linked to each of these values. In the callback, you can create a structure or a table involv...

17 jours ago | 0

Is There a Way to Execute splitapply Functionality on Subtables of Master Table?
you'd better do this way: splitapply(@(x) sum(x, 1), T{:, 2:3}, G);

17 jours ago | 0

HOW TO FIND THE R-SQUARED VALUE
mdl.Rsquared check https://www.mathworks.com/help/stats/linearmodel.html for properties and methods related to linear regressio...

17 jours ago | 0

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What is the reference category in the output for a Fitlme with categorical variables and three-way interaction terms?
The table you copied isn't the default display from matlab, so it's difficult to tell anything from there. It's like an ANOVA ou...

17 jours ago | 0

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Question

Reduce function if concatenated intermediate results doesn't fit in memory
I'm trying to decode a huge dataset of rougly 500k*10k size. What I'm doing is actually load the file into a datastore, replace ...

18 jours ago | 0 answers | 0

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This is a single channel EEG database. Each zip file has 100 txt files. Each txt file has 4096 samples . What does this mean ? ...

18 jours ago | 0

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custom labels for errorplot
using annotation annotation('textbox', pos, 'String', str, 'FitBoxToText', 'on'); pos is the position where you want to put th...

18 jours ago | 0

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How to find the max value of amplitude in Fast Fourier Transform function?
I believe it is correct. you can always test it by plotting them. plot(freq, SSAS); hold on; plot(freq_max, SSAS_max, 'ro'); a...

18 jours ago | 0

MATLAB does not recognize the matrix
qlt_pts = u(kk) * score(kk); your score is a char array. so what do you want this multiplication to give you?

18 jours ago | 0

Converting these 5 lines of MATLAB code to C++?
As creating a vector that increments by 3. So is the first line creating an array of values that starts at one, increments by 2,...

18 jours ago | 0

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How can I check if a table contains numbers only?
I guess your question re the x-values isn't quite clear. For the first part of your question, it is tricky to determine whether...

18 jours ago | 1

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read table handling column of number values as column of strings
you could call detectImpactOptions first, and modify format from there before readtable. https://www.mathworks.com/help/matlab/...

environ un mois ago | 0

Incremental indexing to create an array
using diag(list_of_distances, -1) to get the diagonal you want.

environ un mois ago | 1

| accepted

audio extraction from individual/selective data column.
% it seems from the screenshot that your data is n by 2 matrix % thus length(data) only gives you n % endSample = length(data)...

environ un mois ago | 0

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Sort a cell array based on average of one cell column/row, then sort the structure
I thought I answered this question... anyway, this is less clearer than the other one you asked. See example below % generated ...

environ un mois ago | 0

Export many data into the same excel file.
for i = 1 : nExtracted_files [data,samp_rate] = audioread(Extracted_files(i).name); % different files may have d...

environ un mois ago | 0

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Mean of cell array containing matrices
Not sure what do you mean by "re-sort the cell array according to the means" as you have two means corresponding to each cell. B...

environ un mois ago | 0

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How to explore off diagonal elements in matrices without avoiding the for loop?
Not sure if many matrices share the same size. Anyway if you store these matrices in a cell you prob have a chance using cellfun...

environ un mois ago | 0