I have a dataframe with an oddly formatted dates column. I'd like to create a column just showing the year from the original date column and I am having trouble coming up with a way to do this because the current date column is being treated as a factor. Any advice on how to do this efficiently would be appreciated.
Example
starting with:
org <- c("a","b","c","d")
country <- c("1","2","3","4")
date <- c("01-09-14","01-10-07","11-31-99","10-31-12")
toy <- data.frame(cbind(org,country,date))
toy
org country date
1 a 1 01-09-14
2 b 2 01-10-07
3 c 3 11-31-99
4 d 4 10-31-12
str(toy$date)
Factor w/ 4 levels "01-09-14","01-10-07",..: 1 2 4 3
Desired result:
org country Year
1 a 1 2014
2 b 2 2007
3 c 3 1999
4 d 4 2012
This should work:
transform(toy,Year=format(strptime(date,"%m-%d-%y"),"%Y"))
This produces
## org country date Year
## 1 a 1 01-09-14 2014
## 2 b 2 01-10-07 2007
## 3 c 3 11-31-99 <NA>
## 4 d 4 10-31-12 2012
I initially thought that the NA value was because the %y format indicator wasn't smart enough to handle previous-century dates, but ?strptime says:
‘%y’ Year without century (00-99). On input, values 00 to 68 are
prefixed by 20 and 69 to 99 by 19 - that is the behaviour
specified by the 2004 and 2008 POSIX standards, but they do
also say ‘it is expected that in a future version the default
century inferred from a 2-digit year will change’.
implying that it should be able to handle it.
The problem is actually that 31 November doesn't exist ...
(You can drop the date column at your leisure ...)
Related
I have the following panel data in R:
ID_column<- c("A","A","A","A","B","B","B","B")
Date_column<-c(20040131, 20041231,20051231,20061231, 20051231, 20061231, 20071231, 20081231)
Price_column<-c(12,13,17,19,35,38,39,41)
Data<- data.frame(ID_column, Date_column, Price_column)
#The data looks like this:
ID_column Date_column Price_column
1: A 20040131 12
2: A 20041231 13
3: A 20051231 17
4: A 20061231 19
5: B 20051231 35
6: B 20061231 38
7: B 20071231 39
8: B 20081231 41
My next aim would be to convert the Date column which is currently in a numeric YYYYMMDD format into YYYY by simply taking the first four digits of each entry in the data column as follows:
Data$Date_column<- substr(Data$Date_column,1,4)
#The data then looks like:
ID_column Date_column Price_column
1 A 2004 12
2 A 2004 13
3 A 2005 17
4 A 2006 19
5 B 2005 35
6 B 2006 38
7 B 2007 39
8 B 2008 41
My ultimate goal would be to employ the plm package for panel data regression, but when applying the package and using pdata.frame to set the ID and Time variables as indices, I get error messages of duplicate ID/Time pairs (In this case rows 1 and 2 which would both be given the tag: A,2004). To solve this issue, I would like to delete row 1 in the original data, and only keep the newer observation from the year 2004. This would the provide me with unique ID/Time pairs across the whole data.
Therefore I was hoping for someone to help me out with a loop or a package suggestion with which I can only keep the row with the newer/later observation within a year, if this occurs, also for application to larger data sets.. I believe this involves a couple commands of conditional formatting which I am having difficulties putting together currently. I believe a loop that evaluates whether the first four digits of consecutive date observations are identical and then deletes the one with the "smaller" date/takes the "larger" date would do it, but my experience with loops is very limited.
Kind regards and thank you!
I'd recommend to keep the Date_column as a reference to pick the later observation and mutate a new column for only the year,since you want the latest observation each year.
Data$year<- substr(Data$Date_column,1,4)
> Data$Date_column<- lubridate::ymd(Data$Date_column)
>
> Data %>% arrange(desc(Date_column)) %>%
+ distinct(ID_column,year,.keep_all = TRUE) %>%
+ arrange(Date_column)
ID_column Date_column Price_column year
1 A 2004-12-31 13 2004
2 A 2005-12-31 17 2005
3 B 2005-12-31 35 2005
4 A 2006-12-31 19 2006
5 B 2006-12-31 38 2006
6 B 2007-12-31 39 2007
since we arranged in the actual date in descending order, you guarantee that dropped rows for the unique combination of ID and year is the oldest. you can change the arrangement for the opposite; to get the oldest occuerence
Say you have
Name August September October November
Bob 5 4 3 2
George 3 2 2 4
Gina 1 4 2 1
And you want to convert into 3 columns like so
Name Month Output
Bob August 5
Bob September 4
.....
I see how to do it in VBA through the following link : https://www.extendoffice.com/documents/excel/2773-excel-convert-matrix-to-list.html
Unsure how to execute in R. All of the searching I've yielded want to simply split the matrix into vectors which isn't correct.
If you have a dataframe, say, df you can define its column names as a column in its own right by using names:
df$Month <- names(df)[2:5]
This question already has answers here:
How to reshape data from long to wide format
(14 answers)
Closed 5 years ago.
I'm trying to change a dataframe in R to group multiple rows by a measurement. The table has a location (km), a size (mm) a count of things in that size bin, a site and year. I want to take the sizes, make a column from each one (2, 4 and 6 in this example), and place the corresponding count into each the row for that location, site and year.
It seems like a combination of transposing and grouping, but I can't figure out a way to accomplish this in R. I've looked at t(), dcast() and aggregate(), but those aren't really close at all.
So I would go from something like this:
df <- data.frame(km=c(rep(32,3),rep(50,3)), mm=rep(c(2,4,6),2), count=sample(1:25,6), site=rep("A", 6), year=rep(2013, 6))
km mm count site year
1 32 2 18 A 2013
2 32 4 2 A 2013
3 32 6 12 A 2013
4 50 2 3 A 2013
5 50 4 17 A 2013
6 50 6 21 A 2013
To this:
km site year mm_2 mm_4 mm_6
1 32 A 2013 18 2 12
2 50 A 2013 3 17 21
Edit: I tried the solution in a suggested duplicate, but I did not work for me, not really sure why. The answer below worked better.
As suggested in the comment above, we can use the sep argument in spread:
library(tidyr)
spread(df, mm, count, sep = "_")
km site year mm_2 mm_4 mm_6
1 32 A 2013 4 20 1
2 50 A 2013 15 14 22
As you mentioned dcast(), here is a method using it.
set.seed(1)
df <- data.frame(km=c(rep(32,3),rep(50,3)),
mm=rep(c(2,4,6),2),
count=sample(1:25,6),
site=rep("A", 6),
year=rep(2013, 6))
library(reshape2)
dcast(df, ... ~ mm, value.var="count")
# km site year 2 4 6
# 1 32 A 2013 13 10 20
# 2 50 A 2013 3 17 1
And if you want a bit of a challenge you can try the base function reshape().
df2 <- reshape(df, v.names="count", idvar="km", timevar="mm", ids="mm", direction="wide")
colnames(df2) <- sub("count.", "mm_", colnames(df2))
df2
# km site year mm_2 mm_4 mm_6
# 1 32 A 2013 13 10 20
# 4 50 A 2013 3 17 1
I have data organized by two ID variables, Year and Country, like so:
Year Country VarA VarB
2015 USA 1 3
2016 USA 2 2
2014 Canada 0 10
2015 Canada 6 5
2016 Canada 7 8
I'd like to keep Year as an ID variable, but create multiple columns for VarA and VarB, one for each value of Country (I'm not picky about column order), to make the following table:
Year VarA.Canada VarA.USA VarB.Canada VarB.USA
2014 0 NA 10 NA
2015 6 1 5 3
2016 7 2 8 2
I managed to do this with the following code:
require(data.table)
require(reshape2)
data <- as.data.table(read.table(header=TRUE, text='Year Country VarA VarB
2015 USA 1 3
2016 USA 2 2
2014 Canada 0 10
2015 Canada 6 5
2016 Canada 7 8'))
molten <- melt(data, id.vars=c('Year', 'Country'))
molten[,variable:=paste(variable, Country, sep='.')]
recast <- dcast(molten, Year ~ variable)
But this seems a bit hacky (especially editing the default-named variable field). Can I do it with fewer function calls? Ideally I could just call one function, specifying the columns to drop as IDs and the formula for creating new variable names.
Using dcast you can cast multiple value.vars at once (from data.table v1.9.6 on). Try:
dcast(data, Year ~ Country, value.var = c("VarA","VarB"), sep = ".")
# Year VarA.Canada VarA.USA VarB.Canada VarB.USA
#1: 2014 0 NA 10 NA
#2: 2015 6 1 5 3
#3: 2016 7 2 8 2
I have the following dataframe
y<-data.frame(c(2007,2008,2009,2009,2010,2010),c(10,13,10,11,9,10),c(5,6,5,7,4,7))
colnames(y)<-c("year","a","b")
I want to have a final data.frame that adds together within the same year the values in "y$a" in the new "a" column and the values in "y$b" in the new "b" column so that it looks like this"
year a b
2007 10 5
2008 13 6
2009 21 12
2010 19 11
The following loop has done it for me,
years<- as.numeric(levels(factor(y$year)))
add.a<- numeric(length(y[,1]))
add.b<- numeric(length(y[,1]))
for(i in years){
ind<- which(y$year==i)
add.a[ind]<- sum(as.numeric(as.character(y[ind,"a"])))
add.b[ind]<- sum(as.numeric(as.character(y[ind,"b"])))
}
y.final<-data.frame(y$year,add.a,add.b)
colnames(y.final)<-c("year","a","b")
y.final<-subset(y.final,!duplicated(y.final$year))
but I just think there must be a faster command. Any ideas?
Kindest regards,
Marco
The aggregate function is a good choice for this sort of operation, type ?aggregate for more information about it.
aggregate(cbind(a,b) ~ year, data = y, sum)
# year a b
#1 2007 10 5
#2 2008 13 6
#3 2009 21 12
#4 2010 19 11