Create numerous statistical models based on selection criteria in a separate dataframe - r

Question

I want to perform a certain number of statistical models based on selection criteria specified in a dataframe. So using a basic example, say I had 2 responses variables and 2 explanatory variables:
#######################Data Input############################
Responses <- as.data.frame(matrix(sample(0:10, 1*100, replace=TRUE), ncol=2))
colnames(Responses) <- c("A","B")
Explanatories <- as.data.frame(matrix(sample(20:30, 1*100, replace=TRUE), ncol=2))
colnames(Explanatories) <- c("x","y")
I then define which statistical models that I would like to run, which can include different combinations of Response / Explanatory variables and different statistical functions:
###################Model selection#########################
Function <- c("LIN","LOG","EXP") ##Linear, Logarithmic (base 10) and exponential - see the formula for these below
Respo <- c("A","B","B")
Explan <- c("x","x","y")
Model_selection <- data.frame(Function,Respo,Explan)
How do I then perform a list of models based on these selection criteria? Here is an example of the models I would like to create based on the inputs from the Model_selection data frame.
####################Model creation#########################
Models <- list(
lm(Responses$A ~ Explanatories$x),
lm(Responses$B ~ log10(Explanatories$x)),
lm(Responses$B ~ exp(Explanatories$y))
)
I would guess that some kind of loop function would be required and after looking around perhaps paste too? Thanks in advance for any help with this

Answer 1

This isn't the prettiest solution, but it seems to work for your example:
Models <- list()
idx <- 1L
for (row in 1:nrow(Model_selection)){
if (Model_selection$Function[row]=='LOG'){
expl <- paste0('LOG', Model_selection$Explan[row])
Explanatories[[expl]] <- log10(Explanatories[[Model_selection$Explan[row]]])
Models[[idx]] <- lm(Responses[[Model_selection$Respo[row]]] ~ Explanatories[[expl]])
}
if (Model_selection$Function[row]=='EXP'){
expl <- paste0('EXP', Model_selection$Explan[row])
Explanatories[[expl]] <- exp(Explanatories[[Model_selection$Explan[row]]])
Models[[idx]] <- lm(Responses[[Model_selection$Respo[row]]] ~ Explanatories[[expl]])
}
if (Model_selection$Function[row]=='LIN'){
expl <- paste0('LIN', Model_selection$Explan[row])
Explanatories[[expl]] <- Explanatories[[Model_selection$Explan[row]]]
Models[[idx]] <- lm(Responses[[Model_selection$Respo[row]]] ~ Explanatories[[expl]])
}
names(Models)[idx] <- paste(Model_selection$Respo[row], '~', expl)
idx <- idx+1L
}
Models

Answer 2

This is a perfect use-case for the tidyverse
library(tidyverse)
## cbind both data sets into one
my_data <- cbind(Responses, Explanatories)
## use 'mutate' to change function names to the existing function names
## mutate_all to transform implicit factors to characters
## NB this step could be ommitted if Function would already use the proper names
model_params <- Model_selection %>%
mutate(Function = case_when(Function == "LIN" ~ "identity",
Function == "LOG" ~ "log10",
Function == "EXP" ~ "exp")) %>%
mutate_all(as.character)
## create a function which estimates the model given the parameters
## NB: function params must be named exactly like columns
## in the model_selection df
make_model <- function(Function, Respo, Explan) {
my_formula <- formula(paste0(Respo, "~", Function, "(", Explan, ")"))
my_mod <- lm(my_formula, data = my_data)
## syntactic sugar: such that we see the value of the formula in the print
my_mod$call$formula <- my_formula
my_mod
}
## use purrr::pmap to loop over the model params
## creates a list with all the models
pmap(model_params, make_model)