.help parkey Dec90 tables
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NAME
parkey -- Write an IRAF parameter to a header keyword.
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USAGE
parkey value output keyword
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DESCRIPTION
This task changes the value of a header keyword in either a table or an
image. If the value of the task parameter 'add' is "yes", the task will
allow you to add a new keyword to the header, otherwise, adding a new
keyword will cause an error. Type conversion is performed if the data type of
the header keyword differs from the data type of the input parameter 'value'. 
If a new
keyword is added to the file, the type is determined 
from the input value. The
strings "yes", "y", "no", "n", "true", "t", "false", and "f", in either
upper or lower case, are interpreted as boolean values.
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PARAMETERS
.ls value [string]
Input value to be written to the header keyword. (Strings are case sensitive.)
.le
.ls output [file name]
Name of the file whose header keyword is to be changed.
.le
.ls keyword [string]
Name of the header keyword to be changed. (The name is not case sensitive.)
.le
.ls (add = no) [boolean]
Allow new header keywords to be added?  

If 'add = no', then existing keywords
can take new values but no new keywords can be added to the file.
.le
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EXAMPLES
1. Set the header keyword 'OVERSCAN' in the file 'image.hhh' to 5:

.nf
tt> parkey 5 image.hhh overscan
.fi

2. Set the group parameter 'CTYPE1' in the second group of the same
file to "ANGSTROM":

.nf
tt> parkey ANGSTROM image.hhh[2] ctype1
.fi

3. Set the header keyword 'YSTEP' to the value stored 
in the IRAF parameter 'x':

.nf
tt> parkey (x) image.hhh ystep
.fi

4. Add the keyword 'COMPNAME' to the table header and put the value "FILTER1"
in it:

.nf
tt> parkey FILTER1 graph.tab compname add+
.fi
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BUGS
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REFERENCES
This task was written by Bernie Simon.
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SEE ALSO
keypar, keytab, partab, tabkey, tabpar
.endhelp
