[R] How to avoid the three loops in R?
ONKELINX, Thierry
Thierry.ONKELINX at inbo.be
Fri Aug 1 15:40:19 CEST 2014
It is possible to do without loops if you start by calculating the totals. Then is just aggregating and merging data.
Best regards,
Thierry
set.seed(21)
n.country <- 5
average.price <- runif(n.country, max = 200)
price <- expand.grid(
Product = 1:10,
Country = factor(LETTERS[seq_len(n.country)]),
Year = 2000:2010
)
price$Price <- rnorm(nrow(price), mean = average.price[price$Country], sd = 30)
#number and sum of all prices of the product over all countries and years
total.product <- aggregate(
cbind(Price, N = 1) ~ Product,
data = price,
FUN = sum
)
#number and sum of all prices of the product per country over all years
total.product.country <- aggregate(
cbind(Pricec = Price, Nc = 1) ~ Product + Country,
data = price,
FUN = sum
)
#merge both tables
combined.price <- merge(total.product, total.product.country)
with(combined.price, Price / N) #average price
with(combined.price, Pricec / Nc) #average price per country
with(combined.price, (Price - Pricec)/ (N - Nc)) #average price in the other countries
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium
+ 32 2 525 02 51
+ 32 54 43 61 85
Thierry.Onkelinx op inbo.be
www.inbo.be
To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of.
~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data.
~ Roger Brinner
The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey
-----Oorspronkelijk bericht-----
Van: r-help-bounces op r-project.org [mailto:r-help-bounces op r-project.org] Namens PIKAL Petr
Verzonden: vrijdag 1 augustus 2014 15:18
Aan: Lingyi Ma
CC: r-help op r-project.org
Onderwerp: Re: [R] How to avoid the three loops in R?
Hi
I do not see any solution without loops but maybe others find it.
I think that you can do it in one loop. Best structure for loop will be list.
In each cycle you will compute matrix with diagonal NA
mat<-matrix(1,nrow=number of items, ncol=number of items)
diag(mat) <- NA
apply(price chunk * mat, 2, mean, na.rm=T)
So when I named your example as temp I get
fac <- interaction(factor(temp$Product), factor(temp$Year_Month), drop=T) lll <- split(temp, fac) for( i in 1:length(lll)) { mat <- matrix(1, nrow=nrow(lll[[i]]), ncol= nrow(lll[[i]]))
diag(mat) <- NA
lll[[i]]$others <- apply(mat*lll[[i]][,3], 2, mean, na.rm=T) }
> lll
$`1.201204`
Country Product Price Year_Month others
1 AE 1 20 201204 24
2 DE 1 20 201204 24
3 CN 1 28 201204 20
$`2.201204`
Country Product Price Year_Month others
4 AE 2 28 201204 25
5 DE 2 28 201204 25
6 CN 2 22 201204 28
$`3.201204`
Country Product Price Year_Month others
7 AE 3 28 201204 28
8 CN 3 28 201204 28
$`1.201205`
Country Product Price Year_Month others
9 AE 1 20 201205 24
10 DE 1 20 201205 24
11 CN 1 28 201205 20
$`2.201205`
Country Product Price Year_Month others
12 AE 2 28 201205 28
13 DE 2 28 201205 28
I did not check speed but it shall be OK.
Regards
Petr
> -----Original Message-----
> From: r-help-bounces op r-project.org [mailto:r-help-bounces op r-
> project.org] On Behalf Of Lingyi Ma
> Sent: Friday, August 01, 2014 1:42 PM
> To: r-help op r-project.org
> Subject: [R] How to avoid the three loops in R?
>
> I have the following data set:
>
> Country Product Price Year_Month
> AE 1 20 201204
> DE 1 20 201204
> CN 1 28 201204
> AE 2 28 201204
> DE 2 28 201204
> CN 2 22 201204
> AE 3 28 201204
> CN 3 28 201204
> AE 1 20 201205
> DE 1 20 201205
> CN 1 28 201205
> AE 2 28 201205
> DE 2 28 201205
>
> I want to create the one more column which is "The average price of
> the product in other areas".
> in other word, for each month, for each product, I calculate the
> average of such product in the other area.
>
> I want sth like:
>
> Country Product Price Year_Month Price_average_In_Other_area
> AE 1 20 201204 14
> AE 2 28 201204 25
>
> Please avoid the three for loop, I have tried and it never end. I have
> 1070427 rows. Is there better way to speed up my program?
>
> [[alternative HTML version deleted]]
>
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