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pselect noao.digiphot.ptools



pselect - select records from an APPHOT/DAOPHOT database


pselect infiles outfiles expr


The APPHOT/DAOPHOT databases containing the records from which the selection is to be made.
The output APPHOT/DAOPHOT databases containing the selected records.
The boolean expression to be evaluated. The expression is evaluated once for each record. If expr = yes, a copy is made of the input file.


PSELECT selects a subset of the records from an APPHOT/DAOPHOT database or a list of databases and writes the new records out to another database or list of databases.

The output records are selected on the basis of an input boolean expression expr whose variables are in the case of text databases the field names specified by the #N keywords or the parameters specified by the #K keywords and in the case of an STSDAS table database the column names. If after substituting the values associated with a particular record into the field name variables the expression evaluates to yes, that record is included in the output database.

The supported operators and functions are briefly described below. A detailed description of the boolean expression evaluator and its syntax can be found in the manual page for the IMAGES package HEDIT task.

The following logical operators can be used in the boolean expression.

	equal		  ==	not equal		!=
	less than	  <	less than or equal	<=
	greater than	  >	greater than or equal	>=
	or		  ||	and			&&
	negation	  !	pattern match		?=
	concatenation	  //

The pattern match character ?= takes a string expression as its first argument and a pattern as its second argument. The result is yes if the pattern is contained in the string expression. Patterns are strings which may contain pattern matching metacharacters. The metacharacters themselves can be matched by preceeding them with the escape character. The metacharacters are listed below.

	beginning of string	^	end of string		$
	one character		?	zero or more characters	*
	white space		#	escape character	\
	ignore case		{	end ignore case		}
	begin character class	[	end character class	]
	not, in char class	^	range, in char class	-

The boolean expression may also include arithmetic operators and functions. The following arithmetic operators and functions are supported.

addition		+		subtraction		-
multiplication		*		division		/
negation		-		exponentiation		**
absolute value		abs(x)		cosine			cos(x)
sine			sin(x)		tangent			tan(x)
arc cosine		acos(x)		arc sine		asin(x)
arc tangent		atan(x)		arc tangent		atan2(x,y)
exponential		exp(x)		square root		sqrt(x)
natural log		log(x)		common log		log10(x)
minimum			min(x,y)	maximum			max(x,y)
convert to integer	int(x)		convert to real		real(x)
nearest integer		nint(x)		modulo			mod(x)


1. Select the records from the output of the APPHOT CENTER task for which 100. <= XCENTER <= 200. and 300. <= YCENTER <= 400.

    pt> pselect m92.ctr.3 m92out \
	"XCE >= 100. && XCE <= 200. && YCE >= 300. && YCE <= 400."

2. Select the records from the output of the APPHOT PHOT task for which the first magnitude is not equal to INDEF. In the case of the an STDSDAS table database it may be necessary to escape the leading square bracket.

    pt> pselect n4147.mag.3 n4147out "MAG[1] != INDEF"


    pt> pselect n4147.mag.3 n4147out "MAG\[1] != INDEF"

3. Select the records from the output of the DAOPHOT ALLSTAR task for which CHI <= 5.0 and MERR <= .10 magnitudes.

    pt> pselect m92out "CHI <= 5.0 && MERR <= 1.0"


Array valued fields in text databases are not allowed in the expression field.



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