Re: [R] Subsetting dataframe by the nearest values of a vector elements

2015-11-10 Thread Harun Rashid via R-help 
HI Jean,
Here is part of my data. As you can see, I have cross-section point and 
corresponding elevation of a river. Now I want to select cross-section 
points by 50m interval. But the real cross-section data might not have 
exact points say 0, 50, 100,…and so on. Therefore, I need to take points 
closest to those values.

cross_section elevation
1: 5.608 12.765
2: 11.694 10.919
3: 14.784 10.274
4: 20.437 7.949
5: 22.406 7.180
101: 594.255 7.710
102: 595.957 7.717
103: 597.144 7.495
104: 615.925 7.513
105: 615.890 7.751

I checked for some suggestions [particularly here 
]
 
and finally did like this.

intervals <- c(5,50,100,150,200,250,300,350,400,450,500,550,600)
dt = data.table(real.val = w$cross_section, w)
setattr(dt,’sorted’,’cross_section’)
dt[J(intervals), roll = “nearest”]

And it gave me what I wanted.

dt[J(intervals), roll = “nearest”]
cross_section real.val elevation
1: 5 5.608 12.765
2: 50 49.535 6.744
3: 100 115.614 8.026
4: 150 152.029 7.206
5: 200 198.201 6.417
6: 250 247.855 4.497
7: 300 298.450 11.299
8: 350 352.473 11.534
9: 400 401.287 10.550
10: 450 447.768 9.371
11: 500 501.284 8.984
12: 550 550.650 16.488
13: 600 597.144 7.495

I don’t know whether there is a smarter to accomplish this!
Thanks in advance.
Regards,
Harun

On 11/10/15 11:17 AM, David Winsemius wrote:

>> On Nov 9, 2015, at 9:19 AM, Adams, Jean  wrote:
>>
>> Harun,
>>
>> Can you give a simple example?
>>
>> If your cross_section looked like this
>> c(144, 179, 214, 39, 284, 109, 74, 4, 249)
>> and your other vector looked like this
>> c(0, 50, 100, 150, 200, 250, 300, 350)
>> what would you want your subset to look like?
>>
>> Jean
>>
>> On Mon, Nov 9, 2015 at 7:26 AM, Harun Rashid via R-help <
>> r-help@r-project.org> wrote:
>>
>>> Hello,
>>> I have a dataset with two columns 1. cross_section (range: 0~635), and
>>> 2. elevation. The dataset has more than 100 rows. Now I want to make a
>>> subset on the condition that the 'cross_section' column will pick up the
>>> nearest cell from another vector (say 0, 50,100,150,200,.,650).
>>> How can I do this? I would really appreciate a solution.
> If you what the "other vector" to define the “cell” boundaries, and using 
> Jean’s example, it is a simple application of `findInterval`:
>
>> inp <- c(144, 179, 214, 39, 284, 109, 74, 4, 249)
>> mids <- c(0, 50, 100, 150, 200, 250, 300, 350)
>> findInterval( inp, c(mids) )
> [1] 3 4 5 1 6 3 2 1 5
>
> On the other hand ...
>
> To find the number of "closest point", this might help:
>
>
>> findInterval(inp, c( mids[1]-.001, head(mids,-1)+diff(mids)/2, 
>> tail(mids,1)+.001 ) )
> [1] 4 5 5 2 7 3 2 1 6
>
>
>
> —
> David Winsemius
> Alameda, CA, USA
>
​

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Re: [R] Subsetting dataframe by the nearest values of a vector elements

2015-11-09 Thread David Winsemius 

> On Nov 9, 2015, at 9:19 AM, Adams, Jean  wrote:
> 
> Harun,
> 
> Can you give a simple example?
> 
> If your cross_section looked like this
> c(144, 179, 214, 39, 284, 109, 74, 4, 249)
> and your other vector looked like this
> c(0, 50, 100, 150, 200, 250, 300, 350)
> what would you want your subset to look like?
> 
> Jean
> 
> On Mon, Nov 9, 2015 at 7:26 AM, Harun Rashid via R-help <
> r-help@r-project.org> wrote:
> 
>> Hello,
>> I have a dataset with two columns 1. cross_section (range: 0~635), and
>> 2. elevation. The dataset has more than 100 rows. Now I want to make a
>> subset on the condition that the 'cross_section' column will pick up the
>> nearest cell from another vector (say 0, 50,100,150,200,.,650).
>> How can I do this? I would really appreciate a solution.

If you what the "other vector" to define the “cell” boundaries, and using 
Jean’s example, it is a simple application of `findInterval`:

> inp <- c(144, 179, 214, 39, 284, 109, 74, 4, 249)
> mids <- c(0, 50, 100, 150, 200, 250, 300, 350)

> findInterval( inp, c(mids) )
[1] 3 4 5 1 6 3 2 1 5

On the other hand ...

To find the number of "closest point", this might help:


> findInterval(inp, c( mids[1]-.001, head(mids,-1)+diff(mids)/2, 
> tail(mids,1)+.001 ) )
[1] 4 5 5 2 7 3 2 1 6



— 
David Winsemius
Alameda, CA, USA

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Re: [R] Subsetting dataframe by the nearest values of a vector elements

2015-11-09 Thread jim holtman 
Do you want the "closest" or what range it is in?  If you want the range,
then use 'cut':

> x <- c(144, 179, 214, 39, 284, 109, 74, 4, 249)
> range <- c(0, 50, 100, 150, 200, 250, 300, 350)
> result <- cut(x, breaks = range)
> cbind(x, as.character(result))
  x
 [1,] "144" "(100,150]"
 [2,] "179" "(150,200]"
 [3,] "214" "(200,250]"
 [4,] "39"  "(0,50]"
 [5,] "284" "(250,300]"
 [6,] "109" "(100,150]"
 [7,] "74"  "(50,100]"
 [8,] "4"   "(0,50]"
 [9,] "249" "(200,250]"



Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.

On Mon, Nov 9, 2015 at 12:19 PM, Adams, Jean  wrote:

> Harun,
>
> Can you give a simple example?
>
> If your cross_section looked like this
> c(144, 179, 214, 39, 284, 109, 74, 4, 249)
> and your other vector looked like this
> c(0, 50, 100, 150, 200, 250, 300, 350)
> what would you want your subset to look like?
>
> Jean
>
> On Mon, Nov 9, 2015 at 7:26 AM, Harun Rashid via R-help <
> r-help@r-project.org> wrote:
>
> > Hello,
> > I have a dataset with two columns 1. cross_section (range: 0~635), and
> > 2. elevation. The dataset has more than 100 rows. Now I want to make a
> > subset on the condition that the 'cross_section' column will pick up the
> > nearest cell from another vector (say 0, 50,100,150,200,.,650).
> > How can I do this? I would really appreciate a solution.
> > Regards,
> > Harun
> > --
> >
> > 
> > 
> >
> > [[alternative HTML version deleted]]
> >
> > __
> > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
> [[alternative HTML version deleted]]
>
> __
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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Re: [R] Subsetting dataframe by the nearest values of a vector elements

2015-11-09 Thread Adams, Jean 
Harun,

Can you give a simple example?

If your cross_section looked like this
c(144, 179, 214, 39, 284, 109, 74, 4, 249)
and your other vector looked like this
c(0, 50, 100, 150, 200, 250, 300, 350)
what would you want your subset to look like?

Jean

On Mon, Nov 9, 2015 at 7:26 AM, Harun Rashid via R-help <
r-help@r-project.org> wrote:

> Hello,
> I have a dataset with two columns 1. cross_section (range: 0~635), and
> 2. elevation. The dataset has more than 100 rows. Now I want to make a
> subset on the condition that the 'cross_section' column will pick up the
> nearest cell from another vector (say 0, 50,100,150,200,.,650).
> How can I do this? I would really appreciate a solution.
> Regards,
> Harun
> --
>
> 
> 
>
> [[alternative HTML version deleted]]
>
> __
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

[[alternative HTML version deleted]]

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[R] Subsetting dataframe by the nearest values of a vector elements

2015-11-09 Thread Harun Rashid via R-help 
Hello,
I have a dataset with two columns 1. cross_section (range: 0~635), and 
2. elevation. The dataset has more than 100 rows. Now I want to make a 
subset on the condition that the 'cross_section' column will pick up the 
nearest cell from another vector (say 0, 50,100,150,200,.,650).
How can I do this? I would really appreciate a solution.
Regards,
Harun
-- 




[[alternative HTML version deleted]]

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and provide commented, minimal, self-contained, reproducible code.