Suppose we have three independent variables X=(X_1, X_2, X_3), and a dependent variable Y. If we have a regression model as follow
Y = \alpha+\beta_1 X_1 + \beta_2 X_2 + \beta_3 X_3 + \beta_{12} X_1 X_2 + \beta_{23} X_2 X_3 + \epsilon.
Here is an example: There is a data set as follow:
In this, example there are two continuous variables "Y" and "age", a binary variable "Sex" and a categorical with three categories named "Cat3gr".
The simple model is :
Fitmodel<- lm(Y ~ Sex+age+Cat3gr+Sex*Cat3gr*age, data = data)
summary(Fitmodel)
with the result of :
Call:
lm(formula = Y ~ Sex + age + Cat3gr + Sex * Cat3gr * age, data = data)
Residuals:
Min 1Q Median 3Q Max
-3.963 -0.528 0.270 0.850 2.274
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) -2.29563 1.18565 -1.94 0.053 .
SexMale -0.16346 1.74527 -0.09 0.925
age 0.06408 0.03098 2.07 0.039 *
Cat3gr2 -0.65256 1.31432 -0.50 0.620
Cat3gr3 0.12589 1.60637 0.08 0.938
SexMale:Cat3gr2 2.73782 1.91548 1.43 0.153
SexMale:Cat3gr3 1.42120 2.50115 0.57 0.570
SexMale:age 0.00207 0.04619 0.04 0.964
age:Cat3gr2 -0.00546 0.03359 -0.16 0.871
age:Cat3gr3 0.00610 0.04204 0.15 0.885
SexMale:age:Cat3gr2 -0.05389 0.04963 -1.09 0.278
SexMale:age:Cat3gr3 -0.03253 0.06617 -0.49 0.623
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 1.28 on 762 degrees of freedom
(26 observations deleted due to missingness)
Multiple R-squared: 0.0974, Adjusted R-squared: 0.0843
F-statistic: 7.47 on 11 and 762 DF, p-value: 2.85e-12
How can I visualize two different two interaction way in one plot in R?
I know how to visualize two-way interaction or three-way interaction when there is only one term interaction in the model, but no idea how can I visualize two terms of two-way interaction.