prepad y= prepad (x, l) y= prepad (x, l, c) y= prepad (x, l, c, dim) x: Input vector or matrix of real numbers. l: The length of the final prepadded sequence. c: number used for prepadding. dim: The dimension along which the prepadding should happen. y: Output Prepend the scalar value c to the vector x until it is of length l. If c is not given, a value of 0 is used. If length (x) > l, elements from the beginning of x are removed until a vector of length l is obtained. If x is a matrix, elements are prepended or removed from each row. If the optional argument dim is given, operate along this dimension. If dim is larger than the dimensions of x, the result will have dim dimensions.