# Christoph F.

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**Content Feed**

sos2tf: different result in filtfilt by using SOS vs tf

> IIR Butterworth bandpass of order 40 IIR filters with orders this high are fairly susceptible to numerical effects like coe...

oltre 4 anni ago | 1

| accepted

Applied Fft to my temperature sensor readings and don't understand the result

> Is there an explanation for this result, or is it wrong. The result looks correct. The Fourier transform shows a large DC c...

oltre 4 anni ago | 0

| accepted

Why do I get different frequency response using state-space representation and transfer function

124th order recursive filters are iffy, numerically. At this point, the limited precision of even the double datatype can lead t...

oltre 4 anni ago | 1

I am getting error Undefined function or variable, How to solve this error??

The error means MatLAB cannot find the function write_grid_images(). Is it defined in a separate file or in the same file as ...

oltre 4 anni ago | 0

what is wrong in my code trapezoidal rule

Curly brackets {} have a special meaning in MatLAB syntax (usually when you want to work with the cell datatype). If you did ...

circa 5 anni ago | 0

| accepted

Writing large ammount of data over serial is very slow

A baud rate of 250000/s means a transfer rate of roughly 21000 bytes/s. This means sending 960000 bytes will take about 46 secon...

circa 5 anni ago | 0

why are the peaks of FFT of generated signal slighty off?

Multiplying a function with another function can change the frequency content, as this corresponds to convolving the two image f...

circa 5 anni ago | 0

XCORR of two harmonic signals has a triangular shape. Why?

> What can be the reason of such triangular shape? The reason is that both signals have a significant DC component/offset. Tr...

circa 5 anni ago | 1

How can i use Moving Average Filter to change the sampling rate of a signal!?

You filter the signal and then you reduce the sampling rate. In the most simple case: X=filter([0.5 0.5], 1, X); % Two-e...

circa 5 anni ago | 0

| accepted

Why does the code output something that's clearly false?

> Why is this happening? Look at the value of Ai-AT MatLAB uses numeric methods to invert matrices with inv(), and nu...

circa 5 anni ago | 0

| accepted

Designing a Chebyshev type 2 filter directly in the discrete-time domain?

Answering my own question: The missing criterion is indeed related to the maximum flatness - the second derivative of the sq...

circa 5 anni ago | 0

| accepted

Question

Designing a Chebyshev type 2 filter directly in the discrete-time domain?

I am trying to design a Chebyshev type 2 filter in the discrete-time domain in order to have control over the placement of the f...

circa 5 anni ago | 1 answer | 0

### 1

answerPlot ECG based on heart rate

> I'm having problems getting the plot to display in seconds rather than samples. It looks like your t vector is in samples ...

circa 5 anni ago | 0

Checking for divisibility?

> Is this a result of rounding error? No, it is the result of a bug. In your while loop, the code inputs a new value for cash...

circa 5 anni ago | 0

What does the error Attempted to access k(3e-10); index must be a positive integer or logical. mean?

k(a+b) means to MatLab "the (a+b)th element of vector k". However, a+b isn't integer. Maybe the expression cos(k(a+...

circa 5 anni ago | 0

Speed up FIR filter

As an answer: Using filter() instead of filtfilt() to apply the filter will speed up the calculation by an order of magnitude...

circa 5 anni ago | 1

how to smooth Fourier Spectrum of an acceleration-time history

To make the spectrum appear smoother, you can either apply a window function to the signal in the time domain by element-wise mu...

circa 5 anni ago | 0

How can I do a backward only bandpass filter

Reverse the signal vector, apply bandpass filter with the filter() command, reverse the result?

circa 5 anni ago | 0

I have question of FFT(fast fourier transform)

A Fourier transform decomposes a time-domain signal into sinusoidal components. The frequencies of the sinusoidal components are...

circa 5 anni ago | 1

How to count if loops

count=0 loopStart=1 loopEnd=6 while loopStart < loopEnd count = ...

circa 5 anni ago | 0

| accepted

Finding the exponential of a very small number

> This is not right. Is is as close to the correct answer as can be represented with the 64-bit floating point format that Ma...

circa 5 anni ago | 2

Code Optimization, for loop

Two suggestions: The inner loop only loops from Tmin to (m-1). The extra comparison of m and i inside the loop could be remov...

circa 5 anni ago | 0

| accepted

Get time signal back after NFFT

The time vector as as many elements as X, and they are spaced 1/(f(2)-f(1)) apart. And you will probably need to reverse the ...

circa 5 anni ago | 0

detect QRS signal from ekg shield

If the ECG is noisy, the first place to look for issues would be the circuitry and the connection to the patient. Electrode cont...

circa 5 anni ago | 1

The output of my PID controller is coming very high...

Without more information, perhaps the simulink diagram, the question will be difficult to answer. In general, PID controllers...

circa 5 anni ago | 0

How can I remove noise from my graph?

The most straightforward option is using a filter to remove the noise. This works if the noise has a different spectral content ...

circa 5 anni ago | 0

Want to use Matlab similar to Solver in Excel

I think you're looking for the fminsearch() function. Or alternatively something from the curve fitting toolbox.

circa 5 anni ago | 0

get inverse fourier Optimization, how can i do?

The "clean" solution would be to use MATLABs fft()/ifft() functions. They are optimized and also work for vector sizes that are ...

circa 5 anni ago | 0

How concatenate several signals

> If I do x = [x ; x ], x is a row vector. To concatenate row vectors, use x=[x x] [x; x] creates a 2-by-lenght(x) m...

circa 5 anni ago | 0

Why is MATLAB officially written with capitalized letters?

Because it's a trademark (and hence should be recognizable)?

circa 5 anni ago | 1