Proc Glm, Slice command with one class variable and three continuous variables - contrast effect

[Lena_PA]

Hello 

I would like to test the variable "beta", "gamma", and "alpha" (these are continuous variables) in two different level of "pet_type". Pet_type is a class variable with two values: "dog" or "cat". Ultimately, I would like to have a graph something like this 

my code is 

proc glm data = have ;
class pet_type ;
model logsale = beta gamma alpha pet_type pet_type*beta pet_type*gamma pet_type*alpha/ss3;
lsmeans pet_type*gamma/ slice = pet_type;
lsmeans pet_type*beta/ slice = pet_type;
lsmeans pet_type*alpha/ slice = pet_type;
run;

but I've got an error message that "only CLASS variables allowed in this effect." Please help! 

[Ksharp]

Since LSMEANS compare the mean of Y in two or more groups within CLASS variable, like ANOVA . You should use CATEGORY variable in it.
lsmeans pet_type*gamma/ slice = pet_type;
-->
lsmeans pet_type/ diff ;

[Lena_PA]

Thank you for letting me know! Pet_type is a category variable but alpha, beta, and gamma are not.. so what do you suggest?

[Ksharp]

If You want to check the difference of ALPHA within a category variable,you should check this :

https://support.sas.com/kb/38/384.html