User`s guide

Standard Deviation
5-418
5Standard Deviation
Purpose Find the standard deviation of an input or sequence of inputs.
Library Statistics
Description The Standard Deviation block computes the standard deviation of each column
in the input, or tracks the standard deviation of a sequence of inputs over a
period of time. The
Running standard deviation parameter selects between
basic operation and running operation.
Basic Operation
When the Running standard deviation check box is not selected, the block
computes the standard deviation of each column in M-by-N input matrix
u
independently at each sample time.
y = std(u) % Equivalent MATLAB code
For convenience, length-M 1-D vector inputs and sample-based length-M row
vector inputs are both treated as M-by-1 column vectors. (A scalar input
generates a zero-valued output.)
The output at each sample time,
y, is a 1-by-N vector containing the standard
deviation for each column in
u. For purely real or purely imaginary inputs, the
standard deviation of the jth column is the square root of the variance
where µ
j
is the mean of jth column. For complex inputs, the output is the total
standard deviation for each column in
u, which is the square root of the total
variance for that column.
Note that the total standard deviation is not equal to the sum of the real and
imaginary standard deviations. The frame status of the output is the same as
that of the input.
y
j
σ
j
u
ij
µ
j
–
2
i 1=
M
∑
M 1–
-----------------------------------==
1 jN≤≤
σ
j
σ
jRe,
2
σ
jIm,
2
+=