[R] Is there a funct to sum differences?

arthur brogard abrogard at yahoo.com
Sat Dec 24 22:24:11 CET 2016

```
Hello John,

Here I am back again. Having learned no maths yet but I've looked over the
results here and they are what I am after.

Now I'll try to understand how you did it.

:)

----- Original Message -----
From: "Fox, John" <jfox at mcmaster.ca>
To: arthur brogard <abrogard at yahoo.com>
Cc: Jeff Newmiller <jdnewmil at dcn.davis.ca.us>; "r-help at r-project.org" <r-help at r-project.org>
Sent: Sunday, 25 December 2016, 0:55
Subject: RE: [R] Is there a funct to sum differences?

Dear Arthur,

Here's a simple script to do what I think you want. I've applied it to a contrived example, a vector of the squares of the integers 1 to 25, and have summed the first 5 differences, but the script is adaptable to any numeric vector and any maximum lag. You'll have to decide what to do with the last maximum-lag (in my case, 5) entries:

-------------- snip ------------
> (x <- (1:25)^2)
[1]   1   4   9  16  25  36  49  64  81 100 121 144 169 196 225 256 289 324 361 400 441 484 529 576
[25] 625
> len <- length(x)
> maxlag <- 5
> diffs <- matrix(0, len, maxlag)
> for (lag in 1:maxlag){
+     diffs[1:(len - lag), lag] <- diff(x, lag=lag)
+ }
[,1] [,2] [,3] [,4] [,5]
[1,]    3    8   15   24   35
[2,]    5   12   21   32   45
[3,]    7   16   27   40   55
[4,]    9   20   33   48   65
[5,]   11   24   39   56   75
[6,]   13   28   45   64   85
> tail(diffs)
[,1] [,2] [,3] [,4] [,5]
[20,]   41   84  129  176  225
[21,]   43   88  135  184    0
[22,]   45   92  141    0    0
[23,]   47   96    0    0    0
[24,]   49    0    0    0    0
[25,]    0    0    0    0    0
> rowSums(diffs)
[1]  85 115 145 175 205 235 265 295 325 355 385 415 445 475 505 535 565 595 625 655 450 278 143  49
[25]   0
-------------- snip ------------

The script could very simply be converted into a function if this is a repetitive task with variable inputs.

I hope this helps,
John

-----------------------------
John Fox, Professor
McMaster University
Hamilton, Ontario
Web: socserv.mcmaster.ca/jfox

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of arthur
> brogard via R-help
> Sent: December 24, 2016 12:29 AM
> To: Jeff Newmiller <jdnewmil at dcn.davis.ca.us>
> Cc: r-help at r-project.org
> Subject: Re: [R] Is there a funct to sum differences?
>
> Yes, sorry about that.  I keep making mistakes I shouldn't make.
>
>
> You can ignore the finalone. I have been doing other work on this and it comes
> from there. I took the example from the R screen after it had run one of these
> other things that created the finalone.
>
> I guess I was thinking just seeing the data mentioned in the code was be
> enough.
>
> I don't want a function to do the division and multiplication.
>
> It's a function that will ".. automatically sum the difference between the first
>
>  and subsequent to the end of a list? "  that I am looking for.
>
> I will try to explain, I know I often don't make myself clear:
>
> I'm using this diff() function.
>
> This 'diff()' function finds the difference between two adjoining entries and it
> applies itself to the whole list so that in an instant I can have a list of
> differences between any two adjoining.
>
> Then I can have a list of differences between any two with any specified gap -
> 'lag' it is called.
> Using the same function.
>
> Now I have them and do that.  Then I add them together to find the 'lastone'
> which is the total difference for the period.
>
>
> Now here's the point:  that covers a period of two timespans, months, they are.
>
>  if I want to cover a span of 24 months, say, then I would have to write this
> diff() function 24 times.
>
>  what I'm doing is finding the difference between the starting point and every
> other point and then adding them all together.  bit like finding the area
> beneath the curve maybe.
>
>  And that's what I want to do.
>
>  :)
>
>
>
>
>
>
>
>
>
> ----- Original Message -----
> From: Jeff Newmiller <jdnewmil at dcn.davis.ca.us>
> To: arthur brogard <abrogard at yahoo.com>
> Cc: r-help at r-project.org
> Sent: Saturday, 24 December 2016, 15:34
> Subject: Re: [R] Is there a funct to sum differences?
>
> You need to "reply all" so other people can help as well, and others can learn
>
> I am still puzzled by how you expect to compute "finalone". If you had supplied
> numbers other than all 5's it might have been easier to figure out what is going
> on.
>
> What is your purpose in performing this calculation?
>
> #### reproducible code
> rates <- read.table( text =
> "Date          Int
> Jan-1959        5
> Feb-1959        5
> Mar-1959        5
> Apr-1959        5
> May-1959        5
> Jun-1959        5
> Jul-1959        5
> Aug-1959        5
> Sep-1959        5
> Oct-1959        5
> Nov-1959        5
> ", header = TRUE, colClasses = c( "character", "numeric" ) )
>
> rates\$thisone <- c(diff(rates\$Int), NA)
> rates\$nextone <- c(diff(rates\$Int, lag=2), NA, NA) rates\$lastone <-
> (rates\$thisone + rates\$nextone)/6.5*1000 # I doubt there is a ready-built
> function that knows you want to # divide by 6.5 or multiply by 1000
>
> # form a vector from positions 2:11 and append NA)
> rates\$experiment1 <- rates\$Int + c( rates\$Int[ -1 ], NA ) # numbers that are not
> all the same
> rates\$Int2 <- (1:11)^2
> rates\$experiment2 <- rates\$Int2 + c( rates\$Int2[ -1 ], NA )
>
> # dput(rates)
> result <- structure(list(Date = c("Jan-1959", "Feb-1959", "Mar-1959", "Apr-
> 1959", "May-1959", "Jun-1959", "Jul-1959", "Aug-1959", "Sep-1959", "Oct-
> 1959", "Nov-1959"), Int = c(5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5), thisone = c(0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, NA), nextone = c(0, 0, 0, 0, 0, 0, 0, 0, 0, NA, NA), lastone = c(0, 0, 0,
> 0, 0, 0, 0, 0, 0, NA, NA), Int2 = c(1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121),
> experiment1 = c(10, 10, 10, 10, 10, 10, 10, 10, 10, 10, NA), experiment2 = c(5,
> 13, 25, 41, 61, 85, 113, 145, 181, 221, NA)), .Names = c("Date", "Int",
> "thisone", "nextone", "lastone", "Int2", "experiment1", "experiment2"),
> row.names = c(NA, -11L), class = "data.frame")
>
> On Sat, 24 Dec 2016, arthur brogard wrote:
>
> >
> >
> > Yes, sure, thanks for your interest.  I apologise for not submitting in the
> correct manner.  I'll learn (I hope).
> >
> > Here's the source - a spreadsheet with just two columns, date and 'Int'.
> >
> >
> > Date    Int
> > Jan-1959    5
> > Feb-1959    5
> > Mar-1959    5
> > Apr-1959    5
> > May-1959    5
> > Jun-1959    5
> > Jul-1959    5
> > Aug-1959    5
> > Sep-1959    5
> > Oct-1959    5
> > Nov-1959    5
> >
> >
> > After processing it becomes this:
> >
> >
> >> rates
> > Date   Int thisone nextone     lastone finalone
> > 1   1959-01-01  5.00    0.00    0.00    0.000000       10
> > 2   1959-02-01  5.00    0.00    0.00    0.000000       10
> > 3   1959-03-01  5.00    0.00    0.00    0.000000       10
> > 4   1959-04-01  5.00    0.00    0.00    0.000000       10
> > 5   1959-05-01  5.00    0.00    0.00    0.000000       10
> > 6   1959-06-01  5.00    0.00    0.00    0.000000       10
> >
> > The one long column I'm referring to is the 'Int' column which R has imported.
> >
> > The actual code is:
> >
> >
> > TRUE,colClasses=c("character","numeric"))
> >
> > sapply(rates,class)
> >
> > rates\$Date <- strptime(paste0("1-", rates\$Date), format="%d-%b-%Y",
> > tz="UTC")
> >
> >
> > rates\$thisone <- c(diff(rates\$Int), NA) rates\$nextone <-
> > c(diff(rates\$Int, lag=2), NA, NA) rates\$lastone <- (rates\$thisone +
> > rates\$nextone)/6.5*1000
> >
> >
> > rates
> >
> >
> >
> > ab
> >
> >
> >
> > ----- Original Message -----
> > From: Jeff Newmiller <jdnewmil at dcn.davis.ca.us>
> > To: arthur brogard <abrogard at yahoo.com>; arthur brogard via R-help
> > <r-help at r-project.org>; "r-help at r-project.org" <r-help at r-project.org>
> > Sent: Saturday, 24 December 2016, 13:25
> > Subject: Re: [R] Is there a funct to sum differences?
> >
> > Could you make your example reproducible? That is, include some sample
> input and output. You talk about a column of numbers and then you seem to
> work with named lists and I can't reconcile your words with the code I see.
> > --
> > Sent from my phone. Please excuse my brevity.
> >
> >
> > On December 23, 2016 3:40:18 PM PST, arthur brogard via R-help <r-help at r-
> project.org> wrote:
> >> I've been looking but I can't find a function to sum difference.
> >>
> >> I have this code:
> >>
> >>
> >> rates\$thisone <- c(diff(rates\$Int), NA) rates\$nextone <-
> >> c(diff(rates\$Int, lag=2), NA, NA) rates\$lastone <- (rates\$thisone +
> >> rates\$nextone)
> >>
> >>
> >> It is looking down one long column of numbers.
> >>
> >> It sums the difference between the first two and then between the
> >> first and third and so on.
> >>
> >> Can it be made to automatically sum the difference between the first
> >> and subsequent to the end of a list?
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >
>
> ---------------------------------------------------------------------------
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>
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