| Re: Excluding Decimal Places in the Values of a Variable [message #83204] |
Tue, 19 February 2013 12:32 |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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On 02/14/13 15:55, David Fanning wrote:
>
> I would do it this way:
>
> IDL> x=[[1.35679, 2.65487], [3.65789, 4.56455]]
> IDL> x = Fix(x*1000)/1000.
>
> Cheers,
>
> David
How's this for a more complicated answer:
FUNCTION SetDP, x, n, double=double
num = 10L^n
rnum = KEYWORD_SET(double) ? DOUBLE(num) : FLOAT(num)
RETURN, FLOOR(x*num)/rnum
END
IDL> x=[[1.35679, 2.65487], [3.65789, 4.56455]]
IDL> print, x
1.35679 2.65487
3.65789 4.56455
IDL> print, SetDP(x,2), format='(f18.15)'
1.350000023841858
2.650000095367432
3.650000095367432
4.559999942779541
IDL> print, SetDP(x,2,/double), format='(f18.15)'
1.350000000000000
2.650000000000000
3.650000000000000
4.560000000000000
:o)
Sorry....
cheers,
paulv
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| Re: Excluding Decimal Places in the Values of a Variable [message #83233 is a reply to message #83204] |
Thu, 14 February 2013 13:49  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Gianguido Cianci writes:
> Another simple question: why fix() and not floor()? it seems like the difference is a return type of INT vs LONG. anything else?
I was wondering that myself. My rule on "simple solutions" is to go with
the first one that enters my head. ;-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: Excluding Decimal Places in the Values of a Variable [message #83234 is a reply to message #83233] |
Thu, 14 February 2013 13:41 |
cgguido
Messages: 195
Registered: August 2005
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Senior Member |
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Another simple question: why fix() and not floor()? it seems like the difference is a return type of INT vs LONG. anything else?
Gianguido
On Thursday, February 14, 2013 2:55:56 PM UTC-6, David Fanning wrote:
>
>
> I would do it this way:
>
>
>
> IDL> x=[[1.35679, 2.65487], [3.65789, 4.56455]]
>
> IDL> x = Fix(x*1000)/1000.
>
>
>
> Cheers,
>
>
>
> David
>
>
>
> --
>
> David Fanning, Ph.D.
>
> Fanning Software Consulting, Inc.
>
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
>
> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: Excluding Decimal Places in the Values of a Variable [message #83235 is a reply to message #83234] |
Thu, 14 February 2013 13:31 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Lisa08 writes:
> Wow, so simple and easy. I always make things more complicated than they have to be. Thanks so much!
Oh, sorry. When you said "I have a question that I think should be very
simple to answer" I thought you were looking for the simple solution.
I'll give you the more complicated on next time. ;-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: Excluding Decimal Places in the Values of a Variable [message #83236 is a reply to message #83235] |
Thu, 14 February 2013 13:17 |
Lisa08
Messages: 4
Registered: February 2013
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Junior Member |
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On Thursday, February 14, 2013 2:55:56 PM UTC-6, David Fanning wrote:
> Lisa08 writes:
>
>
>
>>
>
>> Hi everyone,
>
>>
>
>> I have a question that I think should be very simple to answer but I can't seem to find a solution for it.
>
>>
>
>> I am trying to chop off the last two decimal places for the values of a variable. The values for my variable have 5 decimal places and I want to trim it down to 3. For example, let's say my variable is:
>
>>
>
>> x=[[1.35679, 2.65487], [3.65789, 4.56455]]
>
>>
>
>> So I want to exclude the last two decimal places and have it be:
>
>>
>
>> x=[[1.356, 2.654], [3.657, 4.564]]
>
>>
>
>>
>
>> Now, I know how to do this using a "PRINT" command as below but I don't know how to tell IDL to save the output that was printed out to a variable.
>
>>
>
>>
>
>> IDL> print, x, FORMAT='(F8.3)'
>
>> 1.357
>
>> 2.655
>
>> 3.658
>
>>
>
>> Also, Is there a way to make it "not round up"? I have found a routine that does what I want, excludes the final two decimal places and doesn't round up, but the problem with it is that it converts the values to a string to do this and then I can't seem to convert them back to floats as it gives me the following error:
>
>>
>
>> Type Conversion error: Unable to convert given STRING to Float
>
>>
>
>> The routine I found online to do this is called DECIMALS.pro and is available here:
>
>>
>
>> https://people.ok.ubc.ca/erosolo/idl/lib/decimals.pro
>
>
>
> I would do it this way:
>
>
>
> IDL> x=[[1.35679, 2.65487], [3.65789, 4.56455]]
>
> IDL> x = Fix(x*1000)/1000.
>
>
>
> Cheers,
>
>
>
> David
>
>
>
> --
>
> David Fanning, Ph.D.
>
> Fanning Software Consulting, Inc.
>
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
>
> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
Wow, so simple and easy. I always make things more complicated than they have to be. Thanks so much!
Lisa
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| Re: Excluding Decimal Places in the Values of a Variable [message #83237 is a reply to message #83236] |
Thu, 14 February 2013 12:55 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Lisa08 writes:
>
> Hi everyone,
>
> I have a question that I think should be very simple to answer but I can't seem to find a solution for it.
>
> I am trying to chop off the last two decimal places for the values of a variable. The values for my variable have 5 decimal places and I want to trim it down to 3. For example, let's say my variable is:
>
> x=[[1.35679, 2.65487], [3.65789, 4.56455]]
>
> So I want to exclude the last two decimal places and have it be:
>
> x=[[1.356, 2.654], [3.657, 4.564]]
>
>
> Now, I know how to do this using a "PRINT" command as below but I don't know how to tell IDL to save the output that was printed out to a variable.
>
>
> IDL> print, x, FORMAT='(F8.3)'
> 1.357
> 2.655
> 3.658
>
> Also, Is there a way to make it "not round up"? I have found a routine that does what I want, excludes the final two decimal places and doesn't round up, but the problem with it is that it converts the values to a string to do this and then I can't seem to convert them back to floats as it gives me the following error:
>
> Type Conversion error: Unable to convert given STRING to Float
>
> The routine I found online to do this is called DECIMALS.pro and is available here:
>
> https://people.ok.ubc.ca/erosolo/idl/lib/decimals.pro
I would do it this way:
IDL> x=[[1.35679, 2.65487], [3.65789, 4.56455]]
IDL> x = Fix(x*1000)/1000.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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