row one of IL down the right edge of a strip of paper using the same spacing as for the observations. [...] Key Method Now write row two of MD on a strip of paper and proceed as before. If we continue this process with all the rows of Mn we will get a new vector zn whose elements are linear transformations of the observation vector y, The dimension of z,, is the same as that of y. Similarly form znBl from Zn and &-I . Continuing this process we finally obtain z1 = z which is the desired interaction vector. In…Expand Abstract