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Re: Am I having a blackout? [message #66646 is a reply to message #66645]

Fri, 29 May 2009 02:14

Allan Whiteford
Messages: 117
Registered: June 2006

Senior Member

Mark wrote:
> Hi all,
>
> I'm trying to read a very simple file with very basic commands, but it
> reads the wrong values for the last variable (d2): readf does not see
> it are negative values and reads only the last five digits. The first
> five items it reads OK. I guess I'm making a very trivial mistake
> here, but I don't see it. Anyone having a clearer mind than me?
> Thanks!
>
> Mark
>
> sum1 = 0.0
> sum2 = 0.0
> sum3 = 0.0
> sum4 = 0.0
> count = 0
> dummy1=''
> openr, unit, /get_lun, 'sunny_days.fits'
> while ~eof(unit) do begin
> readf, unit, format='(A8,F,F,F,F,F)', dummy1, dummy2, A, beta, d1,
> d2

Mark,

My understanding of simply using 'F' as a format code doesn't mean "read
a floating point number in a smart way" it means "use the default values
for a floating point number". These are (according to the manual)
equivalent to 'F15.7'.

So, when you write:

format='(A8,F,F,F,F,F)'

this is equivalent to:

format='(A8,F15.7,F15.7,F15.7,F15.7,F15.7)',

A cursory glance at your file seems to explain what is happening, all
your whitespace are being slowly eaten until finally things go wrong at
the last column.

The behaviour of 'F' doesn't seem to be as useful as you would
reasonably expect it to be.

You probably want to use:

format='(A8,5F13)'

but when reading data in like this it's usually better not to supply a
format code at all - then IDL will try to do something smart for you
based on the types of variables you're using.

Thanks,

Allan

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[Message index]

		Re: Am I having a blackout? By: Brian Larsen on Fri, 29 May 2009 05:31
		Re: Am I having a blackout? By: Allan Whiteford on Fri, 29 May 2009 02:14
		Re: Am I having a blackout? By: Mark[2] on Fri, 29 May 2009 01:25
		Re: Am I having a blackout? By: rogass on Fri, 29 May 2009 00:27
		Re: Am I having a blackout? By: Mark[2] on Thu, 28 May 2009 14:34

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