| Re: array problems [message #61292] |
Fri, 11 July 2008 12:59  |
pgrigis
Messages: 436
Registered: September 2007
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Senior Member |
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jschwab@gmail.com wrote:
> On Jul 11, 2:36 pm, "David Sheerin" <davidshee...@btinternet.com>
> wrote:
>> Hi All
>> I have a palindromic vector of floats, e.g. [a,b,c,b,a] , and I would like
>> to expand it to include the mean between each value like [(0+a)/2, a,
>> (a+b)/2, b, (b+c)/2, c, (c+b)/2, b, (b+a)/2, a, (a+0)/2]. Is there any
>> elegant way of doing this without having to resort to clunky for loops?
>>
>> I also would like to repeat this action on the resulting vector.
>>
>> Thanks for any tips
>>
>> David
>
> Or, even better, just use interpol.
>
> if
> array = [a, b, c, b, a]
> then
> output = interpol(array, 9)
kudos for the oneliner!
Paolo
> is your desired result
>
> Josiah
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| Re: array problems [message #61293 is a reply to message #61292] |
Fri, 11 July 2008 12:26  |
jschwab@gmail.com
Messages: 30
Registered: December 2006
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Member |
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On Jul 11, 2:36 pm, "David Sheerin" <davidshee...@btinternet.com>
wrote:
> Hi All
> I have a palindromic vector of floats, e.g. [a,b,c,b,a] , and I would like
> to expand it to include the mean between each value like [(0+a)/2, a,
> (a+b)/2, b, (b+c)/2, c, (c+b)/2, b, (b+a)/2, a, (a+0)/2]. Is there any
> elegant way of doing this without having to resort to clunky for loops?
>
> I also would like to repeat this action on the resulting vector.
>
> Thanks for any tips
>
> David
Or, even better, just use interpol.
if
array = [a, b, c, b, a]
then
output = interpol(array, 9)
is your desired result
Josiah
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| Re: array problems [message #61294 is a reply to message #61293] |
Fri, 11 July 2008 12:02 |
Jean H.
Messages: 472
Registered: July 2006
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Senior Member |
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David Sheerin wrote:
> Hi All
> I have a palindromic vector of floats, e.g. [a,b,c,b,a] , and I would like
> to expand it to include the mean between each value like [(0+a)/2, a,
> (a+b)/2, b, (b+c)/2, c, (c+b)/2, b, (b+a)/2, a, (a+0)/2]. Is there any
> elegant way of doing this without having to resort to clunky for loops?
>
> I also would like to repeat this action on the resulting vector.
>
> Thanks for any tips
>
> David
>
>
Hi,
1) get your "average".
nbEntries = n_elements(data)
avg = (data + shift(data,-1)) /2.0
2)add the 1st entry and correct the last entry:
avg = [data[0] / 2.0,avg]
avg[nbEntries] = data[nbEntries-1] / 2.0
3)create the new array by coping each original array, with a "step" of 2
cells betweens two values from the same original array
newData = fltarr(nbEntries*2+1)
nnewData[1:nbEntries*2:2] = data
newData[0:nbEntries*2:2] = avg
Jean
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| Re: array problems [message #61295 is a reply to message #61294] |
Fri, 11 July 2008 12:20 |
jschwab@gmail.com
Messages: 30
Registered: December 2006
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Member |
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On Jul 11, 2:36 pm, "David Sheerin" <davidshee...@btinternet.com>
wrote:
> Hi All
> I have a palindromic vector of floats, e.g. [a,b,c,b,a] , and I would like
> to expand it to include the mean between each value like [(0+a)/2, a,
> (a+b)/2, b, (b+c)/2, c, (c+b)/2, b, (b+a)/2, a, (a+0)/2]. Is there any
> elegant way of doing this without having to resort to clunky for loops?
>
> I also would like to repeat this action on the resulting vector.
>
> Thanks for any tips
>
> David
You can do this in a few lines with a combination of rebin and shift.
;; Take only the first section of the array
half = [a, b, c]
;; use rebin with the sample keyword to duplicate your values
;; this gives [a, a, b, b, c, c]
n = n_elements(half)
doubled = rebin(half, 2 * n, /sample)
;; now use shift to combine and average, and drop the last element
extended = ((doubled + shift(doubled, -1)) / 2.0)[0:2*n-2]
;; now you can use reverse() and array concatenation to do back
;; to the full palindromic array
Josiah
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| Re: array problems [message #61296 is a reply to message #61294] |
Fri, 11 July 2008 12:03 |
Vince Hradil
Messages: 574
Registered: December 1999
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Senior Member |
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On Jul 11, 1:36 pm, "David Sheerin" <davidshee...@btinternet.com>
wrote:
> Hi All
> I have a palindromic vector of floats, e.g. [a,b,c,b,a] , and I would like
> to expand it to include the mean between each value like [(0+a)/2, a,
> (a+b)/2, b, (b+c)/2, c, (c+b)/2, b, (b+a)/2, a, (a+0)/2]. Is there any
> elegant way of doing this without having to resort to clunky for loops?
>
> I also would like to repeat this action on the resulting vector.
>
> Thanks for any tips
>
> David
Sounds like you want to look into SHIFT()
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| Re: array problems [message #61366 is a reply to message #61293] |
Mon, 14 July 2008 08:16 |
Bob[3]
Messages: 60
Registered: December 2006
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Member |
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On Jul 11, 3:26 pm, "jsch...@gmail.com" <jsch...@gmail.com> wrote:
> On Jul 11, 2:36 pm, "David Sheerin" <davidshee...@btinternet.com>
> wrote:
>
>> Hi All
>> I have a palindromic vector of floats, e.g. [a,b,c,b,a] , and I would like
>> to expand it to include the mean between each value like [(0+a)/2, a,
>> (a+b)/2, b, (b+c)/2, c, (c+b)/2, b, (b+a)/2, a, (a+0)/2]. Is there any
>> elegant way of doing this without having to resort to clunky for loops?
>
>> I also would like to repeat this action on the resulting vector.
>
>> Thanks for any tips
>
>> David
>
> Or, even better, just use interpol.
>
> if
> array = [a, b, c, b, a]
> then
> output = interpol(array, 9)
> is your desired result
>
> Josiah
Don't forget to add in the first and last elements.
output2 = [output[0]/2, output, output[0]/2] - or similar.
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| Re: array problems [message #61417 is a reply to message #61366] |
Tue, 15 July 2008 12:24 |
David Sheerin
Messages: 4
Registered: April 1999
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Junior Member |
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Great - this is an elegant solution...
Thanks!
"Bob Crawford" <Snowman42@gmail.com> wrote in message
news:8d9523e8-2690-4408-89fb-3f2caed198be@25g2000hsx.googleg roups.com...
On Jul 11, 3:26 pm, "jsch...@gmail.com" <jsch...@gmail.com> wrote:
> On Jul 11, 2:36 pm, "David Sheerin" <davidshee...@btinternet.com>
> wrote:
>
>> Hi All
>> I have a palindromic vector of floats, e.g. [a,b,c,b,a] , and I would
>> like
>> to expand it to include the mean between each value like [(0+a)/2, a,
>> (a+b)/2, b, (b+c)/2, c, (c+b)/2, b, (b+a)/2, a, (a+0)/2]. Is there any
>> elegant way of doing this without having to resort to clunky for loops?
>
>> I also would like to repeat this action on the resulting vector.
>
>> Thanks for any tips
>
>> David
>
> Or, even better, just use interpol.
>
> if
> array = [a, b, c, b, a]
> then
> output = interpol(array, 9)
> is your desired result
>
> Josiah
Don't forget to add in the first and last elements.
output2 = [output[0]/2, output, output[0]/2] - or similar.
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