std
              Compute the standard deviation of the elements of x.
std (x) returns the standard
 deviation of the elements in x defined as
 $$ {\rm std}(x) = \sqrt{{1\over N-1} \sum_{i=1}^N |x_i - \bar x |^2} $$
   where  is the length of the x vector.
 std (x) returns a row vector with
 the standard deviation of each column in x.
 std (x) operates
 along the first non-singleton dimension of x.
  std (x, w) specifies a weighting scheme.  When w = 0
 (default), the standard deviation is normalized by N-1 (population standard
 deviation), where N is the number of observations.  When w = 1, the
 standard deviation is normalized by the number of observations (sample
 standard deviation).  To use the default value you may pass an empty input
 argument [] before entering other options.
w can also be an array of non-negative numbers. When w is a vector, it must have the same length as the number of elements in the operating dimension of x. If w is a matrix or n-D array, or the operating dimension is supplied as a vecdim or "all", w must be the same size as x. NaN values are permitted in w, will be multiplied with the associated values in x, and can be excluded by the nanflag option.
 std (x, [], dim) returns the standard deviation along the
 operating dimension dim of x.  For dim greater than
 ndims (x), then s is returned as zeros of the same size as
 x and m = x.
 std (x, [], vecdim) returns the standard deviation over
 the dimensions specified in the vector vecdim.  For example, if x
 is a 2-by-3-by-4 array, then var (x, [1 2]) returns a
 1-by-1-by-4 array.  Each element of the output array is the standard
 deviation of the elements on the corresponding page of x.
 If vecdim indexes all dimensions of x, then it is equivalent to
 std (x, "all").  Any dimension in vecdim greater than
 ndims (x) is ignored.
 std (x, "all") returns the standard deviation of all the
 elements in x.  The optional flag "all" cannot be used together with
 dim or vecdim input arguments.
 std (…, nanflag) specifies whether to exclude NaN values
 from the calculation using any of the input argument combinations in previous
 syntaxes.  The default value for nanflag is "includenan", and keeps NaN
 values in the calculation. To exclude NaN values, set the value of
 nanflag to "omitnan".
 [s, m] = std (…) also returns the mean of the
 elements of x used to calculate the standard deviation.  If s is
 the weighted standard deviation, then m is the weighted mean.
Source Code: std