| number of decimals? [message #41751] |
Wed, 08 December 2004 20:49  |
Y.T.
Messages: 25
Registered: December 2004
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Junior Member |
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I've almost decided that the following is impossible in IDL, but I
figured I'd give it one more try...
I have a large dblarray of numbers -- say ten by ten million or so:
IDL> f = dblarr(10,1e7)
IDL> f = 1000.*randomn(seed,1e8)
(In reality these are real data values, not random numbers, of course).
I'd like to write these to a file (in the sense of a printf) with an
accuracy of two digits behind the decimal point. I COULD do something
like the following:
IDL> printf,unit,f,format='(10f9.2)'
but that'll introduce additional spaces wherever a number is smaller
than 10000. So a typical line might look like this:
123.45 678.23 1.23 12345.67 ...
etc
But what I want is
123.45 678.23 1.23 12345.67 ...
What I'm trying to do would be written in C somewhat like this: "%.2f
%.2f %.2f", i.e. a floating point number with two decimals.
The help tells me that I can specify the total width as zero to obtain
a "natural width" but if I do a "f0.2" in the above example, I get
things like
123.450000000 678.23000000 1.23000000 12345.6700000000 ...
I have looked into the %"... form of the 'format' keyword but that only
supports "%w.n" forms, not "%.n" forms.
For now, I am doing something unspeakably ugly like this:
printf,strcompress(string(f,format='(10f9.2)'))
which is reasonably workable as long as f is less than about 1/4 of my
total memory -- otherwise the various conversion start swapping and all
hell breaks loose.
I understand that I could do this simply line by line with strcompress,
but that takes approximately a metric forever.
Is there some trick or something that allows me to write a number with
two decimals and "just the right number of digits" before the decimal
point?
Thanks in advance...
cordially
Y.T.
--
Remove YourClothes before you email me.
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| Re: number of decimals? [message #41987 is a reply to message #41751] |
Thu, 09 December 2004 07:23  |
JD Smith
Messages: 850
Registered: December 1999
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Senior Member |
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On Thu, 2004-12-09 at 08:56 +0000, Christopher Lee wrote:
> In article <1102567764.693437.32940@c13g2000cwb.googlegroups.com>,
> "Unknown" <ytyourclothes@p.zapto.org> wrote:
>
>> ...
>> IDL> printf,unit,f,format='(10f9.2)'
>> but that'll introduce additional spaces wherever a number is smaller
>> than 10000. So a typical line might look like this: 123.45 678.23
>> 1.23 12345.67 ... etc
>> But what I want is
>> 123.45 678.23 1.23 12345.67 ...
>> What I'm trying to do would be written in C somewhat like this: "%.2f
>> %.2f %.2f", i.e. a floating point number with two decimals.
>> ...
>> Y. T.
>
> No tricks, but you can use the C format codes in IDL
>
> f=randomn(seed, 10,10)
> print, format='(10(%"%0.5f "))',f[0,*]
>
> That will write out floating point numbers with 5 decimal places and a
> single space between each number. Your emacs loving
> friends will disown you for breaking their copy-rectangle-to-register,
> but I think it's what you want.
For most versions of IDL, your example doesn't work works because 6 is
the default number of decimal places for "natural length" floats, which
is all the "%0.5" requests (i.e. you could have written %0.100). It's
the same with normal format codes, in IDL 6.0:
IDL> print,FORMAT='(2(F0.2,:," "))',!PI,!PI^4
3.141593 97.409103
Starting with IDL6.1, IDL finally respects width "0" formats:
IDL 6.1:
IDL> print,FORMAT='(2(F0.2,:," "))',!PI,!PI^4
3.14 97.41
I hadn't appreciated that you could mix FORTRAN style and C-style format
codes, which could be very useful.
JD
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| Re: number of decimals? [message #41998 is a reply to message #41751] |
Thu, 09 December 2004 00:56 |
Chris Lee
Messages: 101
Registered: August 2003
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Senior Member |
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In article <1102567764.693437.32940@c13g2000cwb.googlegroups.com>,
"Unknown" <ytyourclothes@p.zapto.org> wrote:
> ...
> IDL> printf,unit,f,format='(10f9.2)'
> but that'll introduce additional spaces wherever a number is smaller
> than 10000. So a typical line might look like this: 123.45 678.23
> 1.23 12345.67 ... etc
> But what I want is
> 123.45 678.23 1.23 12345.67 ...
> What I'm trying to do would be written in C somewhat like this: "%.2f
> %.2f %.2f", i.e. a floating point number with two decimals.
> ...
> Y. T.
No tricks, but you can use the C format codes in IDL
f=randomn(seed, 10,10)
print, format='(10(%"%0.5f "))',f[0,*]
That will write out floating point numbers with 5 decimal places and a
single space between each number. Your emacs loving
friends will disown you for breaking their copy-rectangle-to-register,
but I think it's what you want.
Chris.
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