"the dot product of 2 vectors must be a scalar quantity."
Yes.
"I have two vectors P and Z and they both have 6138 data points. So i converted them to Matrix of dimension 6138x3."
Why did you convert one/both of the vectors to matrices?
If both P and Z have 6138 data points, where do all of the 6138*3=18414 data points come from?
"Now when I used dot(P,Z) I am getting a 1x3 matrix."
Which matches exactly what the dot documentation states: "If A and B are matrices or multidimensional arrays, then they must have the same size. In this case, the dot function treats A and B as collections of vectors. The function calculates the dot product of corresponding vectors along the first array dimension whose size does not equal 1."
Lets try it (based on the documentation the expected output will be a 1x3 vector):
A = rand(6138,3);
B = rand(6138,3);
dot(A,B)
