Create a matrix from a list of variables.
A number of commands in Dataplot operate on a matrix. The
CREATE MATRIX command can be a convenient way to create a
matrix from a list of variables.
This command has a similar function to the MATRIX DEFINITION
command. The distinction is that the MATRIX DEFINITION
command creates a matrix from variables that are stored
contiguously in the Dataplot variable space (variables
are stored in the order that they are created). The
CREATE MATRIX command does not impose this restriction.
LET <mat1> = CREATE MATRIX <var1> ... <vark>
where <var1> ... <vark> is a list of 1 to 30
previously defined variables;
<mat1> is a matrix where the resulting matrix is saved;
and where the <SUBSET/EXCEPT/FOR qualification> is optional (and
rarely used in this context).
LET C = CREATE MATRIX X0 X1 X2 X3 X4
The columns of a matrix are accessible as variables by appending
an index to the matrix name. For example, the 4x4 matrix C has
columns C1, C2, C3, and C4. These columns can be operated on
like any other DATAPLOT variable.
The original variables are not deleted. This command creates
new copies of the variables.
To create a matrix from a list of variables without creating
a duplicate copy of the variables, do something like the
WRITE TEMP.OUT X0 X1 X2 X3 X4
DELETE X0 X1 X2 X3 X4
READ MATRIX TEMP.OUT X
Be aware that the variable names are now X1, X2, X3, X4, and X5.
The maximum size matrix that DATAPLOT can handle is set when
DATAPLOT is built on a particular site. Enter the command
HELP MATRIX DIMENSION for details on the maximum size matrix
that can be accomodated.
= Create a matrix from contiguous variables.
= Compute the catcher matrix.
VARIANCE INFLATION FACTORS
= Compute variance inflation factors.
= Compute condition indices.
= Compute the (X'X)**(-1) matrix.
DIMENSION 100 COLUMNS
READ HALD647.DAT Y X1 X2 X3 X4
LET N = SIZE X1
LET X0 = SEQUENCE 1 1 N
LET Z = CREATE MATRIX X0 X1 X2 X3 X4
LET C = CONDITION INDICES Z
Date created: 8/6/2002
Last updated: 4/4/2003
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