Reference Guide

Full Command and Function Reference 3-181
PSDEV
Type: Command
Description: Population Standard Deviation Command: Calculates the population standard deviation of each
of the m columns of coordinate values in the current statistics matrix (reserved variable ΣDAT).
PSDEV returns a vector of m real numbers, or a single real number if m = 1. The population
standard deviation is computed using this formula:
1
n
---
x
k
x–( )
2
k 1=
n
∑
where x
k
is the kth coordinate value in a column,
x
is the mean of the data in this column, and n
is the number of data points.
Access: …µ PSDEV
Input/Output:
Level 1/Argument 1 Level 1/Item 1
→
x
psdev
→
[ x
psdev1
x
psdev2
... x
psdevm
}
See also: MEAN, PCOV, PVAR, SDEV, TOT, VAR
PSI
Type: Function
Description: Calculates the polygamma function, the nth derivative of the digamma function, at a point a.
PSI(a, 0) is equivalent to Psi(a).
Access: !´L SPECIAL
Input: Level 2/Argument 1: A real or complex expression specifying the point a.
Level 1/Argument 2: A non-negative integer, n.
Output: The value of the polygamma function PSI(a, n).
Flags: Exact mode must be set (flag –105 clear), and
numeric mode must not be set (flag –3 clear), if symbolic results are wanted.
Complex mode must be set (flag –103 set) if a complex value is used for point a.
See also: Psi
Psi
Type: Function
Description: Calculates the digamma function at a point a. The digamma function is the derivative of the
natural logarithm (ln) of the gamma function. The function can be represented as follows:
Ψ z( )
d
dz
-----
Γ z( )ln( )
Γ
′
z( )
Γ z( )
------------= =
Access: !´ L SPECIAL
Input: A real or complex expression specifying the point a.
Output: The digamma function at the specified point.
Flags: Exact mode must be set (flag –105 clear), and
numeric mode must not be set (flag –3 clear), if symbolic results are wanted. For example, with
these settings, Psi(3) evaluates to the symbolic value Psi(3).
Complex mode must be set (flag –103 set) if a complex value is used for point a.
See also: PSI