R create a column by concatenating all other columns in R dataframe

Question

I have a data frame with say 20 columns, I would like to create another column that concatenates all other columns, is there a concise way to write the code without expicity writing out each column's column name?

For example my data call model_spec looks like:

this is my current solution: it worked but the problem is that it's very hard=coded and what if I have 100 variables? is there way to achieve this automatically and concatenate all columns without ugly-looking code of explicitly writing out each column name? Thanks in advance! any advice or point to method/function is appreciated!

want = model_spec %>% mutate(
  model_formula = paste0('y ~' , var1 ,'+', var2, '+',var3,'+',var4,'+',var5,
                         '+',var6,'+',var7, '+',var8,'+',var9,'+',var10,
                         '+',var11,'+',var12,'+',var13,'+',var14,'+',var15,'+',var16,'+', 
                         var17,'+',var18, '+', var19, '+', var20))
  ) %>% select(model_id, model_formula)

Answer 1

We could do something like this:

library(dplyr)
library(tidyr)

df %>% 
  unite("new_col", var1:var6, na.rm=TRUE, sep = " + ") %>% 
  mutate(new_col = paste0("y ~ ", new_col))

  model_id                 new_col
1        1 y ~ gdp + ur + dpi + ir
2        1      y ~ ur + ltv + dti

data:

df <- structure(list(model_id = c(1L, 1L), var1 = c("gdp", NA), var2 = c("ur", 
"ur"), var3 = c(NA, "ltv"), var4 = c("dpi", NA), var5 = c(NA, 
"dti"), var6 = c("ir", NA)), class = "data.frame", row.names = c(NA, 
-2L))