## Frequency analysis for dsolve()...

Dear All,

I am working on ODEs and have obtained the plot for "variable vs time". I would like to know if it is possible and how to analyze those data in the frequency domain.ODEs.mw

Thank you.

Very kind wishes,

Wang Zhe

## letter frequency as function of word length...

Hello. I want to replicate the results of this table in Maple.

My "attempt" uses the inbuilt dictionary, but it will only find the words of length n, not the frequency of letters in each ....

word_length.mw

## How to reduce noise using a Fourier Transform on a...

Hello,

I've got a load of data that contains a lot of noise in the form of sinusoidal interference patterns. This is quite thick and it disturbes what I am trying to look at. I've uploaded a picture to represent what I am trying to show. I know I need a cut-off frequency I just don't know how to implement it. Thank you in advance for your help!

Gambia Man

## How to rescale axis?...

Hi all,

I have recentry constructed Fourier amplitude and Fouier Power graphs which are plotted against the frequency of the oscillations, like the picture below.

I would like to change the frequency scale along the x axis into a period scale in order to Fourier analyse future ODE systems in  terms of period rather than frequency.

But I unsure how to manipulate my code to do so.

Any help would be much apreciated, and the Maple file that I am using is attached.

Fourier_with_Period.mw

## Histogram defaults...

Statistics:-Histogram by default choses the vertical axis such that the area under the histogram is 1 (or something like that). In my work, I invariably need to add "frequencyscale=absolute" to get the scale I need. Is there any way to make this the default? Typing this every time gets so old... I have been looking to something analogous to plots:-setoptions but that doesn't seem to exist for Statistics.

M.D.

## I want to obtain the formula of SINGULAR VALUE of ...

Dear.All

I'm a beginner of Maple 13.

In MATLAB, there is a command 'sigmaplot' which draw the 'SINGULAR VALUE OF SYSTEM H(jw)' over all frequency range.

I want to obtain the function of the 'sigmaplot' graph about frequency variable 'w'.

so I defined matrix A,B,C,D in Maple13.

and specify H like following

H:= Multiply(C,Multiply(Inversematrix(s*IdentityMatrix(8)-A),B))+D

--> It is to express H=C*((sI-A)^-1)*B+D that is the state-space matrix of frequency domain form.

and Maple 13 gave me a very long formular expressed by 's'.

Then I try to 'SingularValues' command

but there came up 'Error Message : Error. (in content/polynom) general case of floats not handled'

I couldn't resolve this problem....

Could you give some advice ?

## Create a count from a list?...

Hi,

r:=[3,3,3,3,4,4,4,3,3,3,3,3,3,3,3,2,4,3,1];

What's the shortest way to create a frequency table from it?

Ie, tells me elements are 1,2,3,4

the corresponding counts are: 1,1,13 and 4

and then if it can return the number with highest counts: 3

Many thanks!

Casper

## How can I turn Tally output into a list of lists?...

I am presently using Tally to read through a list of numbers to try and calculate their frequency, I end up with a list as follows:

frequency := [1 = 6, 2 = 7, 3 = 91, 4 = 10], etc.

Now, I've been given a function that should turn this function into a "list of lists":

[code]
list_of_lists := n -> [ op(n)[1],  op(n)[2] ]
[/code]

As can be expected from looking at this function, it only returns the first two elements from the original list

## Deconstruct a waveform into its fundamental freque...

I have a sample waveform of an air conditioner and want to see if any low frequencies (10 Hz which is harmful to human health) exist in the wave.  How can I do that?

Granted the frequencies picked up in the recorded file depend on the quality of the recording and the recorder and lower frequencies may not have been picked up.

I've looked at

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