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# FW

Last seen: 2 months ago Active since 2017

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Multiplication of large matrix with its transpose
What would be the best way to multiply a large matrix A say, 100000 x 10, by its transpose A' in MATLAB 2021b. The output will b...

12 months ago | 2 answers | 0

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How to obtain orthogonal (not orthonormal) vectors from "orth" or "qr"?
Suppose there is a set of vectors v1, v2, v3, v4 with V=[v1, v2, v3, v4]. The vectors have very large number of data points ~ 10...

12 months ago | 1 answer | 0

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Difference between orth(A) and classical Gram Schmidt
I wanted to know the difference between the classical Gram Schmidt (GS) method and the orth() option in MATLAB. I tried doc and ...

12 months ago | 1 answer | 0

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Using a variable vector in a loop
Hello, I am trying to use a large number of vectors (up to 60) for orthogonalization. Say, we have column vectors, v1, v2, v3,.....

12 months ago | 2 answers | 0

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Reducing the distance among subplot figures?
I am using a subplot option to plot parts of a figure. Is there is a possibility to reduce the distance between the two figures,...

1 year ago | 4 answers | 0

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How to incorporate multiple IF conditions to generate noisy data?
Hello, I wanted to simulate a signal which has noise in the form of spikes (both positive and negative). If a single IF conditio...

2 years ago | 1 answer | 0

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Error in opening a data file with cdf extension
I have been sent data file with a .cdf extension. It is supposed to contain time and light absorbance data. When I use the cdfre...

2 years ago | 0 answers | 0

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Question

How to generate a vector of a shifted impulse function?
Hello, Suppose we have a time vector x=0:0.1: 50. I would like to have a delta function at a non-zero position, say at 25 with u...

2 years ago | 1 answer | 0

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How to extract certain rows and columns with the readtable option for Excel files.
Suppose we have an Excel file Data.xlsx. The file have certain descriptive text in the initial rows and then there is tabular da...

3 years ago | 1 answer | 0

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How to convert or extract arrays from a structure?
In continuous wavelet analysis, when we export the coefficients into the workspace, the data is exported as a structure (1x1 str...

3 years ago | 1 answer | 0

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Question

Integration via trapezoidal rule in various sections of the same array
If the signal S consists of several peaks as a function of time, is there a way to assign integration limits for the trapezoidal...

3 years ago | 1 answer | 0

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Question

Generating Approximations from "appcoef" in Wavelet Toolbox
I have a question regarding the MATLAB example for "1-D approximation coefficients" https://www.mathworks.com/help/wavelet/ref/a...

3 years ago | 0 answers | 0

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Question

How to replace complex numbers in a column vector with 0.000+0.000i ?
Image we obtain a fft of a signal and we wish to remove certain frequencies from the signal. I want to fill in zeros after remov...

3 years ago | 2 answers | 0

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Question

Finding several local maximum values in a given range and corresponding indices
If we have a dataset "y" which consists of a sum of 5 gaussian peaks as function of time t, there will be 5 local maximum value...

3 years ago | 2 answers | 0

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How to locate the index of the maximum value in a given range
Suppose we have two vectors t= [ 1 2 3 4 5 6 7 8 9 10 11]; % time values y = [1 2 3 4 5 7 5 4 3 2 1]; % a dependent variable...

3 years ago | 1 answer | 0

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How to implement a formula involving several elements of the same vector?
Suppose we have two row vectors Time = [ 1 2 3 4 5 6 7 8 9 10]; width= [0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0]; % width of p...

3 years ago | 2 answers | 0

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How to add non-numerical axis values in 3D scatter plots?
I am using a 3D scatter plot option. Can the x-axis values be labeled as "1:1, 2:1, 5:1, 8:1, 10:1" as peak area ratios? Current...

3 years ago | 1 answer | 0

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Question

Reading Selected Columns from an Excel Using the "readtable" Option
If we have an Excel file, and instead of selecting a range of columns, I would like to select certain columns. The following syn...

3 years ago | 1 answer | 0

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Labeling the columns in an array
If we import a .csv or Excel file using readtable, and then convert the table to an array as the following: Data=table2array(re...

3 years ago | 1 answer | 1

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Correct choice of one sided frequency axis after fft
There are a lot of queries on fft frequency. I guess the following point not discussed anywhere explicitly (at least at one plac...

3 years ago | 0 answers | 0

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How to replace numbers in a column vector after certain elements?
How should we proceed if we have a column vector X with 1000 elements, and we wish to replace all the values after a certain row...

3 years ago | 1 answer | 0

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Question

fftshift with even and odd number of data points (scaling the positive and negative frequency axis)
If we wish to draw double sided frequency axis, i.e., positive and negative frequencies with odd and even number of data points ...

3 years ago | 1 answer | 0

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How to add labels to an array or table (after conversion from an array)
I have an array of 2000 x 4 data points. I would like to add labels to the columns only. For example, Column 1 should be 'time/m...

3 years ago | 1 answer | 0

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Question

Assigning indexes in an array and finding max values in a selected range
If we have X = time series data and signal in a 8000x 2 array (Matlab 2017b). The first column is time and the second column is ...

3 years ago | 1 answer | 0

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Question

Frequency scale in fft after zero filling (odd/even number of data)
Product: Matlab 2017b If we have data set "A" which consists of time versus light absorbance.There is another set of data "B"....

3 years ago | 1 answer | 0

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Question

How to combine sections from Workspace into a new vector?
I have Matlab 2017b. 1) If we have two vectors A and B, in the workspace (1000x1), each of same dimension. How can one combine...

3 years ago | 1 answer | 0

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Question

Creating Timetables: Error Message in SampleRate
Hello, I am trying to use a suggested function to generate a timetable with a sampling frequency of 200 Hz. tt = timetable(rand...

3 years ago | 1 answer | 0

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Doing averages in blocks for downsampling time series data
One way to downsample is to do averaging in blocks. I had asked a question here "I would like to downsample data simulated at 20...

3 years ago | 1 answer | 0

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Question

Command for filling in zeros as powers of 2 for FT
If we two sets of signals (A and B) of unequal length, I am using zero padding first to make the length of B equal to A by using...

3 years ago | 1 answer | 0

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Question

How to treat a given column in a sheet from Workspace as a variable?
I am generating exponentially modified Gaussians (EMGs) from a simulation and wish to do FT on a selected sheet in the Workspace...

3 years ago | 0 answers | 0

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