thr3ads.net - R help - [R] Drought severity index: Excel to R [Jan 2010]

If this information is useful, please help other people find it:
Share via:

Muhammad Rahiz

2010-Jan-16 19:57 UTC

[R] Drought severity index: Excel to R

Dear all,

I'm trying to make an R code for the drought severity index (DSI) 
developed by Philips and McGregor (1998). You can refer to the 
description of the algorithm on page 19 from 
http://dissertations.port.ac.uk/229/01/MaloneS.pdf

The code is given in Excel as the following and can be found on page 60 
from the same link.

C7 IF(C6<0,IF(@SUM(A6:A1)<0,C6+A6,"0"),
IF(B7>=0,"0",IF(A6>=0,"0",A6)))

Column A contains the raw anomaly data. Column B contains the 6month 
rolling sum and Column C contains the results of the conditional 
statement which in turn is recycled and input into the conditional 
statement.

I translated the Excel formula into R, but without any success.

x <- as.matrix(read.table("sample.txt")) # where sample.txt
contains
values of anomalies. See page 60

ct <- 6         # sets a 6-month averaging sequence
n  <- ct -1
d <- matrix( ,32,1) # dummy file

# User defined function
  add <- function(x) Reduce("+", x)

for (i in 1:32){
ii <- i + n
a <- i +1

d[[a]] <-

ifelse(d[ii] < 0 && add(x[c(i:ii)]) < 0, d[ii] + x[ii], ( #
condition 1
ifelse(add(x[c((i+1):(ii+1))]) >= 0, 0, ( # condition 2
ifelse(x[ii] >=0,"0", x[ii]))))) # condition 3
}

The way I see it, this is the main problem.

How do I make the data in Excel's Column C in R? Or in other words, how 
do I update the result of the conditional statements into the dummy 
file, d, which I created (which apparently didn't work).

I hope my explanation makes sense.

thanks.


Muhammad

--
Muhammad Rahiz  |  Doctoral Student in Regional Climate Modeling
Climate Research Laboratory, School of Geography & the Environment
Oxford University Centre for the Environment, University of Oxford
South Parks Road, Oxford, OX1 3QY, United Kingdom
Tel: +44 (0)1865-285194  Mobile: +44 (0)7854-625974
Email: muhammad.rahiz at ouce.ox.ac.uk<mailto:muhammad.rahiz at
ouce.ox.ac.uk>

David Winsemius

2010-Jan-16 21:04 UTC

head link

[R] Drought severity index: Excel to R

On Jan 16, 2010, at 2:57 PM, Muhammad Rahiz wrote:
> Dear all,
>
> I'm trying to make an R code for the drought severity index (DSI)  
> developed by Philips and McGregor (1998). You can refer to the  
> description of the algorithm on page 19 from
http://dissertations.port.ac.uk/229/01/MaloneS.pdf
>
> The code is given in Excel as the following and can be found on page  
> 60 from the same link.
>
> C7 > IF(C6<0,IF(@SUM(A6:A1)<0,C6+A6,"0"),
> IF(B7>=0,"0",IF(A6>=0,"0",A6)))
>
> Column A contains the raw anomaly data. Column B contains the 6month  
> rolling sum and Column C contains the results of the conditional  
> statement which in turn is recycled and input into the conditional  
> statement.
>
> I translated the Excel formula into R, but without any success.
>
> x <- as.matrix(read.table("sample.txt")) # where sample.txt
contains
> values of anomalies. See page 60
>
> ct <- 6         # sets a 6-month averaging sequence
> n  <- ct -1
> d <- matrix( ,32,1) # dummy file
>
> # User defined function
> add <- function(x) Reduce("+", x)
>
> for (i in 1:32){
> ii <- i + n
> a <- i +1
>
> d[[a]] <-
>
> ifelse(d[ii] < 0 && add(x[c(i:ii)]) < 0, d[ii] + x[ii], ( #  
> condition 1
Not sure if this helps (because you only referenced a form of the data  
that would require significant manipulation to import correctly and  
I'n not up for that effort), but shouldn't you use the vectorized form  
of the logical conjunction operator, "&" ?
> ifelse(add(x[c((i+1):(ii+1))]) >= 0, 0, ( # condition 2
I think the outer c( ) is superfluous in this and in the prior ifelse  
clause. i:ii is a vector. Putting c() around it only confuses the  
reader.

> ifelse(x[ii] >=0,"0", x[ii]))))) # condition 3
Seems as though you should stick with numeric results. You cannot mix  
numeric and character values in a vector.
> }
>
> The way I see it, this is the main problem.
>
> How do I make the data in Excel's Column C in R? Or in other words,  
> how do I update the result of the conditional statements into the  
> dummy file, d, which I created (which apparently didn't work).
Why not use dput to offer the data to the readership?
>
> I hope my explanation makes sense.
>
> thanks.
>
>
> Muhammad-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

jim holtman

2010-Jan-17 04:18 UTC

head link

[R] Drought severity index: Excel to R

Try this:

DS <- structure(list(anomaly = c(-27.3, 14.4, 29, -38.1, -3.4, 55.1,
-1, 21.9, -10.9, -7.8, -48.2, -44.9, -43.8, -10.3, 44.2, -0.5,
96.7, -32, -0.2, -38.6, 73.6, -17.5, -57.8, 10.7, -33.4, 46.1,
26.7, -37.3, 1.2, 36.3, 39.6, 31), prev6mon = c(NA, NA, NA, NA,
NA, 29.7, 56, 63.5, 23.6, 53.9, 9.1, -91, -133.8, -166, -110.8,
-103.5, 41.4, 54.3, 97.9, 69.6, 99.1, 82.1, -72.4, -29.7, -62.9,
21.7, -25.2, -45.1, 14, 39.6, 112.7, 97.6), DSI = c(NA, NA, NA,
NA, NA, NA, 0, 0, 0, 0, 0, -48.17, -93.08, -136.93, -147.21,
-102.98, -103.47, 0, 0, 0, 0, 0, -17.47, -75.29, -64.57, -98.01,
0, 0, 0, 0, 0, 0), DSIadj = c(NA, NA, NA, NA, NA, NA, 0, 0, 0,
0, 0, 0.06, 0.12, 0.17, 0.18, 0.13, 0.13, 0, 0, 0, 0, 0, 0.02,
0.09, 0.08, 0.12, 0, 0, 0, 0, 0, 0), DSIpct = c(NA, NA, NA, NA,
NA, NA, 0, 0, 0, 0, 0, 6.02, 11.64, 17.12, 18.4, 12.87, 12.94,
0, 0, 0, 0, 0, 2.18, 9.41, 8.07, 12.25, 0, 0, 0, 0, 0, 0), Month structure(c(5L,
4L, 8L, 1L, 9L, 7L, 6L, 2L, 12L, 11L, 10L, 3L, 5L, 4L, 8L, 1L,
9L, 7L, 6L, 2L, 12L, 11L, 10L, 3L, 5L, 4L, 8L, 1L, 9L, 7L, 6L,
2L), .Label = c("April ", "Aug ", "Dec ",
"Feb ", "Jan", "July ",
"June ", "March ", "May ", "Nov ",
"October ", "Sept "), class = "factor"),
   Yr = c(1980L, 1980L, 1980L, 1980L, 1980L, 1980L, 1980L, 1980L,
   1980L, 1980L, 1980L, 1981L, 1981L, 1981L, 1981L, 1981L, 1981L,
   1981L, 1981L, 1981L, 1981L, 1981L, 1981L, 1981L, 1982L, 1982L,
   1982L, 1982L, 1982L, 1982L, 1982L, 1982L)), .Names = c("anomaly",
"prev6mon", "DSI", "DSIadj", "DSIpct",
"Month", "Yr"), class = "data.frame",
row.names = c(NA,
-32L))
DS  # original data
# now only use the first column of data and construct columns B & C
# fill in the 'prev6mon' column using filter and zero the DSI column
DS$prev6mon <- filter(DS$anomaly, rep(1,6), side=1)
DS$DSI <- 0
# iterate since you have to refer to a previous value
for (i in 7:nrow(DS)){
    DS$DSI[i] <- with(DS, {
        if (DSI[i - 1] < 0) {
            if (prev6mon[i - 1] < 0) DSI[i - 1] + anomaly[i - 1]
            else 0
        }
        else {
            if (prev6mon[i] >= 0) 0
            else {
                if (anomaly[i - 1] >= 0) 0
                else anomaly[i - 1]
            }
        }
    })
}



On Sat, Jan 16, 2010 at 2:57 PM, Muhammad Rahiz <
muhammad.rahiz@ouce.ox.ac.uk> wrote:
> Dear all,
>
> I'm trying to make an R code for the drought severity index (DSI)
developed
> by Philips and McGregor (1998). You can refer to the description of the
> algorithm on page 19 from
> http://dissertations.port.ac.uk/229/01/MaloneS.pdf
>
> The code is given in Excel as the following and can be found on page 60
> from the same link.
>
> C7 > IF(C6<0,IF(@SUM(A6:A1)<0,C6+A6,"0"),
> IF(B7>=0,"0",IF(A6>=0,"0",A6)))
>
> Column A contains the raw anomaly data. Column B contains the 6month
> rolling sum and Column C contains the results of the conditional statement
> which in turn is recycled and input into the conditional statement.
>
> I translated the Excel formula into R, but without any success.
>
> x <- as.matrix(read.table("sample.txt")) # where sample.txt
contains values
> of anomalies. See page 60
>
> ct <- 6         # sets a 6-month averaging sequence
> n  <- ct -1
> d <- matrix( ,32,1) # dummy file
>
> # User defined function
>  add <- function(x) Reduce("+", x)
>
> for (i in 1:32){
> ii <- i + n
> a <- i +1
>
> d[[a]] <-
>
> ifelse(d[ii] < 0 && add(x[c(i:ii)]) < 0, d[ii] + x[ii], ( #
condition 1
> ifelse(add(x[c((i+1):(ii+1))]) >= 0, 0, ( # condition 2
> ifelse(x[ii] >=0,"0", x[ii]))))) # condition 3
> }
>
> The way I see it, this is the main problem.
>
> How do I make the data in Excel's Column C in R? Or in other words, how
do
> I update the result of the conditional statements into the dummy file, d,
> which I created (which apparently didn't work).
>
> I hope my explanation makes sense.
>
> thanks.
>
>
> Muhammad
>
> --
> Muhammad Rahiz  |  Doctoral Student in Regional Climate Modeling
> Climate Research Laboratory, School of Geography & the Environment
> Oxford University Centre for the Environment, University of Oxford
> South Parks Road, Oxford, OX1 3QY, United Kingdom
> Tel: +44 (0)1865-285194  Mobile: +44 (0)7854-625974
> Email:
muhammad.rahiz@ouce.ox.ac.uk<mailto:muhammad.rahiz@ouce.ox.ac.uk>
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
>
http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

	[[alternative HTML version deleted]]

Possibly Parallel Threads

Search for more seemingly similar threads

R help - Jan 2010 - Drought severity index: Excel to R

[R] Drought severity index: Excel to R

[R] Drought severity index: Excel to R

[R] Drought severity index: Excel to R

Possibly Parallel Threads