If I have a dataset with variable A, X, Y, and Z and I want to run two linear regressions - both have A as the dependent variable but one has X as the independent variable and the other has Y (note - NOT multiple regression), what can I do?

`lm(A ~ X, Y, df = df)`  doesn't seem to work, and obviously `lm(A ~ X + Y, df = df)` becomes a multiple regression. I can use `lm(A ~ ., - Z, df = df)` but I'm looking for a way that I could pick and choose multiple variables to use as the independent variable. Thanks.