Is rowjoinbyname a more recent command? In the desktop Stata version 16 the code below works, in the virtual machine I have Stata 15.0 and it gives me the error "matrix operation not found".

How can I accomplish the same without using it?

MWE below:

Code:
sysuse auto.dta

reg price weight mpg
mat output = r(table)
mat list output

matrix estimates = output["b",.]
matrix standarderrors = output["se",.]
matrix lowerbound = estimates-1.96*standarderrors
matrix upperbound = estimates+1.96*standarderrors

matrix rowjoinbyname results = estimates lowerbound upperbound