replace a part of data.table with a vector

Question

I have a data table that can be created by

top_m_dt = data.table(future_fip = c(102, 104, 503),
                  model = c("model_1", "model_2", "model_3"),
                  time_period = c("F1", "F2", "F3"),
                  emission = c("emission_1", "emission_2", "emission_3"),
                  top_1_fip = c(666, 666, 666),
                  top_2_fip = c(666, 666, 666),
                  top_3_fip = c(666, 666, 666))

I would like to replace row 1 and columns top_1_fip, top_2_fip, top_3_fip with a set of values, lets say c(10, 20, 30).

None of the followings work:

top_m_dt[1, c("top_1_fip", "top_2_fip", "top_3_fip")] <- 
    as.numeric(analog_dat_F1$analog_NNs_county[1:3])`

OR

top_m_dt[1, 5:7 ] <- list(analog_dat_F1$analog_NNs_county[1:3])[[1]]

OR

top_m_dt[1, (c("top_1_fip", "top_2_fip", "top_3_fip")):= 
             analog_dat_F1$analog_NNs_county[1:3]] `

They all replace 10 in all three locations. any suggestions?

Your example code doesn't run---do you mean to have each of the target_fip and model_n and emission values in quotes? — Gregor Thomas
– Gregor Thomas, Commented May 21, 2019 at 22:44
Sorry, the last parentheses was left out of {code} mode! And, OK, those emissions have values in my computer! so, yeah, lets put quotes on them. sorry. — OverFlow Police
– OverFlow Police, Commented May 21, 2019 at 23:01

Ronak Shah · Accepted Answer · 2019-05-21 23:08:17Z

3

data.table syntax is bit different and not everything that works on a dataframe works on data.table. In this case to replace values from specific row and column you could use as.list

library(data.table)
top_m_dt[1, c("top_1_fip", "top_2_fip", "top_3_fip") := as.list(c(10, 20, 30))]

top_m_dt
#   future_fip   model time_period emission top_1_fip top_2_fip top_3_fip
#1: target_fip model_n          F1 emission        10        20        30
#2: target_fip model_n          F2 emission       666       666       666
#3: target_fip model_n          F3 emission       666       666       666

answered May 21, 2019 at 23:08

Ronak Shah

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1 Comment

OverFlow Police Over a year ago

I was missing as. before the list. This shit is sensitive to everything!

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