- Form: STAT variable=function[expression]
-
- variable
- is a VISTA math variable in which the
value of the statistic is stored.
- expression
- is an arithmetic expression which involves
at least one reference to data in an OPEN'ed ASCII file.
- function
- is one of the following:
- MAX :Find the maximum value of the expression.
- MIN :Find the minimum value of the expression.
- FIRST :Finds the first value of the expression.
- LAST :Find the last value of the expression.
- COUNT :Counts the number of lines in the file.
In this case 'expression' is a logical file name.
- LOAD : Loads the arithmetic expression from each
line in the input file into a specified buffer
using STAT N=LOAD[buffer,expression]
The STAT command can be used to determine information about the data values
in an ASCII file. For the MAX and MIN functions, the given expression is
evaluated for each line in the file. For the FIRST function, the
expression is evaluated for the first line in the file and for the LAST
function the expression is evaluated for the last line in the file. The
COUNT function merely counts the lines in the file. Remember that SKIP'ed
lines (see the SKIP command) are never included in the calculations. These
STAT functions are not the same as the normal VISTA math functions and can
not be included in other mathematical expressions.
The LOAD function allows the user to load data from an input ASCII file
into a VISTA image buffer. Arithmetic operations may be performed on the
input data before loading into the buffer. Simply specify the desired
buffer and the arithmetic expression to load. The new buffer will
automatically be created.
Examples:
- STAT LINES=COUNT[DATAFILE]
- Set the variable LINES to the
number of lines in the file DATAFILE. DATAFILE must have been
opened with the OPEN command. SKIP'ed lines are not counted.
- STAT MAXVAL=MAX[2.5*LOG10[@PHOT.2]]
- Evaluates the
expression 2.5*LOG10[@PHOT.2] for each line in the file PHOT and
sets MAXVAL to have the maximum value. The file PHOT will be left
repositioned to the beginning of the file after the STAT command
completes.
- STAT N=LOAD[1,@PHOT.1*@PHOT.2]
- Loads the product of the
values in the first and second columns of the input file PHOT into
VISTA buffer number 1.