NAG Library Routine Document
X04DCF is an easy-to-use routine to print a
triangular matrix stored in a packed one-dimensional array.
X04DCF prints a
triangular matrix stored in packed form. It is an easy-to-use driver for X04DDF
. The routine uses default values for the format in which numbers are printed, for labelling the rows and columns, and for output record length.
The matrix must be packed by column.
X04DCF will choose a format code such that numbers will be printed with
an , an or a format
code is chosen if the sizes of all the matrix elements to be printed lie between and . The
code is chosen if the sizes of all the matrix elements to be printed lie between and . Otherwise the
code is chosen. The chosen code is used to print each complex element of the matrix with the real part above the imaginary part.
The matrix is printed with integer row and column labels, and with a maximum record length of .
The matrix is output to the unit defined by X04ABF
- 1: UPLO – CHARACTER(1)Input
: indicates the type of the matrix to be printed
- The matrix is lower triangular. In this case, the packed array A holds the matrix elements in the following order: , etc.
- The matrix is upper triangular. In this case, the packed array A holds the matrix elements in the following order: , etc.
- 2: DIAG – CHARACTER(1)Input
: indicates whether the diagonal elements of the matrix are to be printed.
- The diagonal elements of the matrix are not referenced and not printed.
- The diagonal elements of the matrix are not referenced, but are assumed all to be unity, and are printed as such.
- The diagonal elements of the matrix are referenced and printed.
, or .
- 3: N – INTEGERInput
: the order of the matrix to be printed.
is less than
, X04DCF will exit immediately after printing TITLE
; no row or column labels are printed.
- 4: A() – COMPLEX (KIND=nag_wp) arrayInput
the dimension of the array A
must be at least
: the matrix to be printed. Note that A
must have space for the diagonal elements of the matrix, even if these are not stored.
- if , the upper triangle of must be stored with element in for ;
- if , the lower triangle of must be stored with element in for .
If , the diagonal elements of are assumed to be , and are not referenced; the same storage scheme is used whether or ‘U’.
- 5: TITLE – CHARACTER(*)Input
: a title to be printed above the matrix.
If , no title (and no blank line) will be printed.
contains more than
characters, the contents of TITLE
will be wrapped onto more than one line, with the break after
Any trailing blank characters in TITLE
- 6: IFAIL – INTEGERInput/Output
must be set to
. If you are unfamiliar with this parameter you should refer to Section 3.3
in the Essential Introduction for details.
For environments where it might be inappropriate to halt program execution when an error is detected, the value
is recommended. If the output of error messages is undesirable, then the value
is recommended. Otherwise, if you are not familiar with this parameter, the recommended value is
. When the value is used it is essential to test the value of IFAIL on exit.
unless the routine detects an error or a warning has been flagged (see Section 6
6 Error Indicators and Warnings
If on entry
, explanatory error messages are output on the current error message unit (as defined by X04AAF
Errors or warnings detected by the routine:
|On entry,|| or .|
|On entry,||, or .|
A call to X04DCF is equivalent to a call to X04DDF
with the following argument values:
NCOLS = 80
INDENT = 0
LABROW = 'I'
LABCOL = 'I'
FORM = ' '
USEFRM = 'A'
The example program calls X04DCF twice, first to print a by lower triangular matrix, and then to print a by upper triangular matrix.
9.1 Program Text
Program Text (x04dcfe.f90)
9.2 Program Data
9.3 Program Results
Program Results (x04dcfe.r)