Patients and symptoms. Each of a set of N patients can exhibit any number of a set of n symptoms. We express this as an N n matrix S, with S ij = 1...

Patients and symptoms. Each of a set of N patients can exhibit any number of a set of n symptoms. We express this as an N × n matrix S, with Sij = 1 if patient i exhibits symptom j, or 0 otherwise. Give simple English descriptions of the following expressions. Include the dimensions, and describe the entries.

(a) S1.

(b) ST1.

(c) STS.

(d) SST .

(e) IIsi − sjII2, where skT is the kth row of S.