Table of Contents

## How do you plot a spectrogram in MATLAB?

Direct link to this answer

- [s, f, t] = spectrogram(x, w ,noverlap, nfft, Fs);
- % x is the signal; %w is the window;
- % noverlap is the windowing overlap; nfft is the size of fft;
- % and Fs is the samplong rate.
- figure()
- surf(t, f, 20*log10(abs(s)));

## How do you plot fft of a signal in MATLAB?

Plot the pulse in the time domain. To use the fft function to convert the signal to the frequency domain, first identify a new input length that is the next power of 2 from the original signal length. This will pad the signal X with trailing zeros in order to improve the performance of fft . n = 2^nextpow2(L);

**What is spectrum and spectrogram?**

A spectrogram gives a running display of a sound signal as it occurs in real time; a spectrum, on the other hand, gives us a snapshot of the sound at a specific point in time. A spectrum can enable you to see, for example, the energy distribution over the different frequencies of a single vowel, like [i].

**How do you make a spectrogram?**

To construct the spectrogram of a nonstationary signal, Signal Analyzer follows these steps:

- Divide the signal into equal-length segments.
- Window each segment and compute its spectrum to get the short-time Fourier transform.
- Display segment-by-segment the power of each spectrum in decibels.

### Why do we need frequency spectrum?

Spectrum is a range of electromagnetic radio frequencies used for transmission of voice, data and images. Mobile telecom operators send and receive frequencies to enable communication between two phones. The defence services and railways also use the spectrum .

### What is the importance of frequency spectrum?

Having more spectrum helps operators to deliver this better user experience. In particular, aggregating spectrum into larger downlink carriers raises peak data speeds but also more generally helps to provide the higher average speeds valued by many users.

**What is the frequency of a spectrum?**

3.1. Frequency spectrum of a signal is the range of frequencies contained by a signal. For example, a square wave is shown in Fig. 3.5A. It can be represented by a series of sine waves, S(t) = 4A/π sin(2πft) + 4A/3π sin(2π(3f)t) + 4A/5π sin(2π(5f)t + …)

**How do you read a frequency spectrum graph?**

Low frequency peaks are shown at the left end of the graph. The left-most peak represents the fundamental. Other peaks indicate overtones. The height of each peak indicates how much of each frequency is present in the vibration.

## How does MATLAB calculate Fourier spectrum?

y = fft(x); fs = 1/Ts; f = (0:length(y)-1)*fs/length(y); When you plot the magnitude of the signal as a function of frequency, the spikes in magnitude correspond to the signal’s frequency components of 15 Hz and 20 Hz.

## What is spectrogram Matlab?

s = spectrogram( x ) returns the short-time Fourier transform of the input signal, x . Each column of s contains an estimate of the short-term, time-localized frequency content of x . s = spectrogram( x , window ) uses window to divide the signal into segments and perform windowing.

**What is frequency in spectrogram?**

A spectrogram is a visual way of representing the signal strength, or “loudness”, of a signal over time at various frequencies present in a particular waveform. Not only can one see whether there is more or less energy at, for example, 2 Hz vs 10 Hz, but one can also see how energy levels vary over time.

**What is plotted on a spectrogram?**

### How do you use FFT in MATLAB?

In MATLAB®, the fft function computes the Fourier transform using a fast Fourier transform algorithm. Use fft to compute the discrete Fourier transform of the signal. y = fft (x); Plot the power spectrum as a function of frequency.

### How can I analyze the frequency spectrum of audio data?

You can use the Fourier transform to analyze the frequency spectrum of audio data. The file bluewhale.au contains audio data from a Pacific blue whale vocalization recorded by underwater microphones off the coast of California.

**How do I analyze the spectra of a signal?**

You can zoom into signal regions of interest and analyze the spectra at those zoomed regions. 4) If you have split your signals into multiple signal frames you can use the Spectrum Analyzer scope.

**How to view the power spectrum centered at 0 frequency?**

In many applications, it is more convenient to view the power spectrum centered at 0 frequency because it better represents the signal’s periodicity. Use the fftshift function to perform a circular shift on y, and plot the 0-centered power.

## What is contour plot in MATLAB?

contour( Z ) creates a contour plot containing the isolines of matrix Z , where Z contains height values on the x-y plane. MATLAB® automatically selects the contour lines to display. The column and row indices of Z are the x and y coordinates in the plane, respectively.

## How do you plot a 3d contour plot in MATLAB?

Define Z as a function of two variables, X and Y . Then plot the contours of Z . In this case, let MATLAB® choose the contours and the limits for the x- and y-axes. Now specify 50 contour levels, and display the results within the x and y limits used to calculate Z .

**How do you plot an isosurface in MATLAB?**

Plot Isosurface with Lighting Create an isosurface where the isovalue is 0.0001. Compute the locations of the faces and vertices as a structure. Then, plot the face and vertex data by passing the structure data to the patch function. Adjust the view of the plot, change the surface colors, and specify custom lighting.

**How do you plot a frequency spectrum of a signal in Matlab?**

In MATLAB®, the fft function computes the Fourier transform using a fast Fourier transform algorithm. Use fft to compute the discrete Fourier transform of the signal. y = fft(x); Plot the power spectrum as a function of frequency.

### What does a contour plot show?

A contour plot is a graphical technique for representing a 3-dimensional surface by plotting constant z slices, called contours, on a 2-dimensional format. That is, given a value for z, lines are drawn for connecting the (x,y) coordinates where that z value occurs.

### How do you make a contour plot?

In a worksheet, click where you want to insert a contour plot and press Ctrl+5. An empty contour plot region appears. Alternatively, on the Plots tab, in the Traces group, select Contour Plot from the Insert Plot list.

**What is a 3d contour plot?**

Contour plots display the 3-dimensional relationship in two dimensions, with x- and y-factors (predictors) plotted on the x- and y-scales and response values represented by contours. A contour plot is like a topographical map in which x-, y-, and z-values are plotted instead of longitude, latitude, and elevation.

**Can we have multiple 3d plots in MATLAB?**

Can we have multiple 3d plots in MATLAB? Explanation: The plot3() function is a pre-defined function in MATLAB. So, it will allow the use to generate multiple 3d plots. This is inherent to the system.

## What is an isosurface plot?

An isosurface plot is used to extract surfaces of constant w from a function of the form w = f(x, y, z), i.e. it is the 3d equivalent of a contour plot. The data from which the isosurface plots are generated can be defined as a formula (analytical plot), or loaded from a file.

## What is isosurface extraction?

Isosurface extraction is a powerful tool for investigating volumetric scalar fields. An isosurface in a scalar volume is a surface on which the data value is constant, separating regions of higher and lower value.

**How do you plot a frequency distribution in MATLAB?**

Plot Frequency Distribution Curves of Your Data in MATLAB

- Use the sshist() Function to Calculate Density-Estimation and Obtain the Frequency Curve of Our Data in MATLAB.
- Use the histfit() Function to Obtain the Frequency Curve of Our Data in MATLAB.

**How do you plot amplitude and frequency in MATLAB?**

Y = fft(y,NFFT)/L; f = Fs/2*linspace(0,1,NFFT/2+1); subplot(2,1,2); % Plot single-sided amplitude spectrum.

### What is the difference between spectrogram and Mel spectrogram?

A spectrogram is a visualization of the frequency spectrum of a signal, where the frequency spectrum of a signal is the frequency range that is contained by the signal. The Mel scale mimics how the human ear works, with research showing humans don’t perceive frequencies on a linear scale.

### How do you analyze a contour plot?

Use contour plots to display the relationship between two independent variables and a dependent variable. The graph shows values of the Z variable for combinations of the X and Y variables. The X and Y values are displayed along the X and Y-axes, while contour lines and bands represent the Z value.

**Why contour plot is used?**

Contour lines commonly show altitude (like height of a geographical features), but they can also be used to show density, brightness, or electric potential. A contour plot is appropriate if you want to see how some value Z changes as a function of two inputs, X and Y: z = f(x, y).

**How do you smooth a contour plot in MATLAB?**

Choose the “smoothness” of the new plot via the parameter newpoints . A 3D-surf plot would be more suitable for very smooth color-shading. Just rotate it to a top-down view.

## Why do we use contour plots?

Contour plots are particularly helpful when you need to identify combinations of X and Y that produce beneficial or required values of Z. The contour lines and bands make it easy to find combinations that yield the values you need.

Working of Contour Plot in Matlab with Syntax Contour plots are one of the main plots which are used to display the three-dimension figures. They have different syntaxes which are used in Matlab like: contour (X): This is used to draw a contour plot where X contains the values of the height which are defined in the two dimensional (x-y) plane.

## How to create a contour plot using the peaks function?

Create a contour plot of the peaks function. Make the contour lines thicker by setting the LineWidth property to 3. Insert NaN values wherever there are discontinuities on a surface. The contour function does not draw contour lines in those regions. Define matrix Z as a sampling of the peaks function.

**How do I highlight contours at particular levels in MATLAB?**

This example shows how to highlight contours at particular levels. Run the command by entering it in the MATLAB Command Window. Web browsers do not support MATLAB commands. Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: United States.

**How do you make a contour plot thicker in Matplotlib?**

Create a contour plot of the peaks function. Make the contour lines thicker by setting the LineWidth property to 3. Insert NaN values wherever there are discontinuities on a surface. The contour function does not draw contour lines in those regions.