It makes use of the INDIRECT function to convert strings into valid range references and the UNIQUE function to remove duplicate values. Needless to say, I’m not going to break that out line by line, at least not today. Let’s strategize before diving headlong into the formulas and note that:ġ) A single row matrix, 1-by-X, multiplied by a single column matrix of compatible size, X-by-1, will result in a 1-by-1 matrix, i.e.
#Another word for running tota how to#
Now you know how to do matrix multiplication, let’s use that in an array formula example with the MMULT function. Phew, math aside, let’s get back to the more comfortable ground of our Google Sheet. It takes matrices A and B as arguments, =MMULT(A,B), and outputs the matrix product AB. Print exercises and lessons: Hint: For exercises, you can reveal the answers first ('Submit Worksheet') and print the page to have the exercise and theUnit 8 A2 Gateway Test. The MMULT formula does this matrix multiplication for us. Find the total surface area and the volume of a closed cylindrical container with radius 5 cm and a height of 34 cm. (i, k) entry of AB = i th row of A * k th column of B The resulting matrix will have a shape (m, p).Įach entry in the new matrix is defined by the rule In other words if A has shape (m, n) then B must have shape (n, p), for this to work. The product AB of matrices A = (a ij) and B = (b hk) is defined if and only if the number of columns of A equals the number of rows of B. The only definition worth stating here, that pertains to the MMULT function, is this one: Once I got over the initial shock of seeing “Ben Collins 1999” written on the inside cover (yes, I’m really that old!), I flipped to page 192 and reminisced about the good old days… no, I mean I refreshed my mind on the particulars of matrices, particularly their multiplication. It’s been a while since I’ve done matrix multiplication, so I dug out one of my graduate mathematics books: Sets & Groups, A First Course in Algebra by J.A. Wouldn’t it be nice if we could have a single formula at the top of the column to calculate the running total for us?īut first… A quick aside on matrix multiplication
The principal disadvantage of this formula is this need to fill out the entire column with a new formula for each row.