Combine attributes from two columns and sum the values from duplicate rows - r

Question

This question is slightly modified from this one.
I have a dataframe in long table format like this:
df1 <- data.frame(ID=c(1,1,1,1,1,1,2,2),
name=c("a","c","a","c","a","c","a","c"),
value=c("broad",50,"mangrove",50,"mangrove",50,"coniferous",50))
ID name value
1 a broad
1 c 50
1 a mangrove
1 c 50
1 a mangrove
1 c 50
2 a coniferous
2 c 50
About the data: The value from the second row 50 corresponds to the value broad from the first row. Similarly, the value from the fourth row 50 corresponds to the value mangrove from the third row and so on.. In simple words, values for name c are related with name a.
I want to combine the value in such a way that I could get the corresponding values for each name, which would also aggregate the values with similar names:
df2 <- data.frame(ID=c(1,1,2),
name=c("c_broad","c_mangrove","c_coniferous"),
value=c(50,100,50))
which should look like this:
ID name value
1 c_broad 50
1 c_mangrove 100
2 c_coniferous 50

Answer 1

Using reshape2:
library(reshape2)
df1$grp = cumsum(df1$name == "a")
df2 = dcast(df1, ID + grp ~ name)
df2$c = as.numeric(df2$c)
aggregate(c ~ ID + a, df2, sum)
ID a c
1 1 broad 50
2 2 coniferous 50
3 1 mangrove 100
Column names can be changed if desired, also "c_" can be added to the names with paste.

Answer 2

Using tidyverse:
value_a <- df1 %>% dplyr::filter(name=="a") %>% dplyr::pull(value)
df1 %>%
dplyr::filter(name=="c") %>% #Modify into a sensible data frame from here
dplyr::mutate(a = value_a,
name = stringr::str_c(name, "_" ,a)) %>%
dplyr::select(-a) %>% # to here
dplyr::group_by(ID, name) %>%
dplyr::summarise(value=sum(as.numeric(value)))
# A tibble: 3 x 3
# Groups: ID [2]
ID name value
<dbl> <chr> <dbl>
1 1 c_broad 50
2 1 c_mangrove 100
3 2 c_coniferous 50
Tha main problem you find in your dataframe is that a single column is containing, names and values, and that is the first thing you should fix. My advice is always modify the original dataframe into a tidy format (https://tidyr.tidyverse.org/articles/tidy-data.html) and from there leverage all tidyverse power, or data.table or your framework of choice.
Notice the temporal variable value_a could be included in the pipeline directly I have not done it for clarity. The main idea is to separate values and species in different columns, the first three calls in the pipeline, and then apply the usual tidyverse operations.

Answer 3

Might not be the most elegant, but it works:
df1 <- data.frame(ID=c(1,1,1,1,1,1,2,2),
name=c("a","c","a","c","a","c","a","c"),
value=c("broad",50,"mangrove",50,"mangrove",50,"coniferous",50)
)
df1 %>% group_by( 1+floor((1:n()-1)/2) ) %>%
summarize(
ID = ID[1],
name = paste0( name[2], "_", value[1] ),
value = as.numeric(value[2])
) %>% ungroup %>% select( -1 ) %>% group_by(name) %>%
mutate( value = sum(value) ) %>%
unique
Here is somthing improved, that actually is humanly readable:
i <- seq( 1, nrow(df1), 2 )
df1 %>% summarise(
ID = ID[i],
name = paste0( name[i+1], "_", value[i] ),
value = as.numeric(value[i+1])
) %>% group_by(name) %>%
summarize(
ID=ID[1], value = sum( value )
) %>% arrange(ID)

Answer 4

Base R solution:
# Nullify numeric values belonging to a grouping category: grps => character vector
grps <- gsub("\\d+", NA, df1$value)
# Interpolate NA values using prior string value: a => character vector
df1$a <- na.omit(grps)[cumsum(!(is.na(grps)))]
# Split-Apply-Combine aggregation: data.frame => stdout(console)
data.frame(do.call(rbind, lapply(with(df1, split(df1, a)), function(x){
y <- transform(subset(x, !grepl("\\D+", value)), value = as.numeric(value))
setNames(
aggregate(value ~ ID + a, y, FUN = function(z){sum(z, na.rm = TRUE)}),
c("ID", "a", "c")
)
}
)
),
row.names = NULL
)

Answer 5

additional option
df1 <- data.frame(ID=c(1,1,1,1,1,1,2,2),
name=c("a","c","a","c","a","c","a","c"),
value=c("broad",50,"mangrove",50,"mangrove",50,"coniferous",50))
library(tidyverse)
df1 %>%
pivot_wider(ID, names_from = name, values_from = value) %>%
unnest(c("a", "c")) %>%
group_by(ID, name = a) %>%
summarise(value = sum(as.numeric(c), na.rm = T), .groups = "drop")
#> # A tibble: 3 x 3
#> ID name value
#> <dbl> <chr> <dbl>
#> 1 1 broad 50
#> 2 1 mangrove 100
#> 3 2 coniferous 50
Created on 2021-04-12 by the reprex package (v2.0.0)