I am trying to build a linear regression with hundreds of interaction terms. I am now manually typing them into the equation.
model <- lm(Y ~ A B C A*X1 A*X2 A*X3 ... A*X100 B*X1 B*X2 B*X3... B*X100, data)
is there a way to code this more efficiently? I am thinking about something like:
Group <- X1 X2 X3 ... X99 X100
model <- lm(Y~ A B C A*Group B*Group)
Is this possible to be achieved in R with any packages or functions?
CodePudding user response：
You could try:
xs <- paste(paste("X", 1:100, sep=""),collapse=" ")
form1 <- as.formula(sprintf("Y~ C (A B)*(%s)",xs))
model <- lm(form1)
form1
Y ~ C (A B) * (X1 X2 X3 X4 X5 X6 X7 X8 X9
X10 X11 X12 X13 X14 X15 X16 X17 X18 X19
X20 X21 X22 X23 X24 X25 X26 X27 X28 X29
X30 X31 X32 X33 X34 X35 X36 X37 X38 X39
X40 X41 X42 X43 X44 X45 X46 X47 X48 X49
X50 X51 X52 X53 X54 X55 X56 X57 X58 X59
X60 X61 X62 X63 X64 X65 X66 X67 X68 X69
X70 X71 X72 X73 X74 X75 X76 X77 X78 X79
X80 X81 X82 X83 X84 X85 X86 X87 X88 X89
X90 X91 X92 X93 X94 X95 X96 X97 X98 X99
X100)
The first line builds the X1 X2 ... X100 part. The second line creates the formula with A, B and C main effects with A and B crossed with each X. as.formula will turn a string into a formula.
CodePudding user response：
Consider reformulate by building a vector of right-hand side variables and then pass it as first argument:
rhs_vars <- c(
"A", "B", "C",
paste0("A*X", 1:100),
paste0("B*X", 1:100)
)
model <- lm(reformulate(rhs_vars, "Y"), data)
CodePudding user response：
We can use a combination of paste0 and reformulate:
Group <- paste0("X", 1:100)
rhs_expanded<-c(paste0("A*", Group), paste0("B*", Group))
lm_formula<-reformulate(response = 'Y', termlabels = c('A', 'B', 'C', rhs_expanded))
lm(formula = lm_formula, data)
See the lm_formula object that is produced by reformulate:
lm_formula
Y ~ A B C A * X1 A * X2 A * X3 A * X4 A * X5
A * X6 A * X7 A * X8 A * X9 A * X10 A * X11 A *
X12 A * X13 A * X14 A * X15 A * X16 A * X17 A *
X18 A * X19 A * X20 A * X21 A * X22 A * X23 A *
X24 A * X25 A * X26 A * X27 A * X28 A * X29 A *
X30 A * X31 A * X32 A * X33 A * X34 A * X35 A *
X36 A * X37 A * X38 A * X39 A * X40 A * X41 A *
X42 A * X43 A * X44 A * X45 A * X46 A * X47 A *
X48 A * X49 A * X50 A * X51 A * X52 A * X53 A *
X54 A * X55 A * X56 A * X57 A * X58 A * X59 A *
X60 A * X61 A * X62 A * X63 A * X64 A * X65 A *
X66 A * X67 A * X68 A * X69 A * X70 A * X71 A *
X72 A * X73 A * X74 A * X75 A * X76 A * X77 A *
X78 A * X79 A * X80 A * X81 A * X82 A * X83 A *
X84 A * X85 A * X86 A * X87 A * X88 A * X89 A *
X90 A * X91 A * X92 A * X93 A * X94 A * X95 A *
X96 A * X97 A * X98 A * X99 A * X100 B * X1 B *
X2 B * X3 B * X4 B * X5 B * X6 B * X7 B * X8
B * X9 B * X10 B * X11 B * X12 B * X13 B * X14
B * X15 B * X16 B * X17 B * X18 B * X19 B * X20
B * X21 B * X22 B * X23 B * X24 B * X25 B * X26
B * X27 B * X28 B * X29 B * X30 B * X31 B * X32
B * X33 B * X34 B * X35 B * X36 B * X37 B * X38
B * X39 B * X40 B * X41 B * X42 B * X43 B * X44
B * X45 B * X46 B * X47 B * X48 B * X49 B * X50
B * X51 B * X52 B * X53 B * X54 B * X55 B * X56
B * X57 B * X58 B * X59 B * X60 B * X61 B * X62
B * X63 B * X64 B * X65 B * X66 B * X67 B * X68
B * X69 B * X70 B * X71 B * X72 B * X73 B * X74
B * X75 B * X76 B * X77 B * X78 B * X79 B * X80
B * X81 B * X82 B * X83 B * X84 B * X85 B * X86
B * X87 B * X88 B * X89 B * X90 B * X91 B * X92
B * X93 B * X94 B * X95 B * X96 B * X97 B * X98
B * X99 B * X100