# Up-sampling in MATLAB

Interpolation or up-sampling is the specific inverse of decimation. It is a data saving operation, in that all examples of x[n] are available in the extended signal y[n]. Interpolation works by adding (L–1) zero-valued examples for each input sample.

We will be using the interp() function to interpolate a signal. It is used to increase the sample rate of a signal by an integer factor.

Syntax: a = interp(x, r)
Parameter:

• x: input signal
• r: interpolation factor

Return Value: Returns interpolated signal

MATLAB code for interpolation of a signal:

## MATLAB

 `% time vector ` `t = 0 : .00025 : 1; ` ` `  `# input signal ` `x = sin(2 * pi * 50 * t) + sin(2 * pi * 100 * t); ` ` `  `% increase the sample rate of i/p signal by factor of 4 ` `y = interp(x, 4);  ` ` `  `subplot(2, 2, 1); ` ` `  `% plot few samples of the Original signal ` `stem(x(1 : 75))  ` `title(``'Original Signal'``); ` ` `  `subplot(2, 2, 2); ` ` `  `% plots few samples of the up-sampled signal ` `stem(y(1 : 75));  ` `title(``'Interpolated Signal'``); `

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