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description: Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
items: number of decimals?
items: Re: number of decimals?

number of decimals?
type: item
description: 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.
creator: Y.T.
date: 2004-12-09T04:49:24-00:00

Re: number of decimals?
type: item
description: 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.
creator: Chris Lee
date: 2004-12-09T08:56:50-00:00

Re: number of decimals?
type: item
description: 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
creator: JD Smith
date: 2004-12-09T15:23:27-00:00