upfirdn This function upsamples the input data, applies the FIR filter and then downsamples it. y = upfirdn (x, h, p, q) x: The input signal. h: The impulse response of the FIR filter. p: The upsampling factor(default=1) q: The downsampling factor(default=1) This function upsamples the input data in the matrix by a factor of n. Then the upsampled data is FIR filtered. After this, the resultant is downsampled.