Let say I have the following data:

trt 0: 113, 108, 110...
trt 1: 108, 110, 106...
trt 2: 98, 96, 110...
trt 3: 103, 104,107...

How can I construct a linear model base on the data with reference to trt3:

I try the following code: summary(lm (trt 3~ trt 0+ trt 1+ trt 2)) but it isn't what I want. Is there anything wrong here?