AGB 260: Agribusiness Information Technology Arrays and Array Formulas

Useful Chapters in the Textbook Regarding this Lecture  Chapter 17  Chapter 18

Arrays  An array is a collection of items which can easily be represented as cells in Excel spreadsheet.  Arrays in Excel can be one or two dimensional which correspond to the rows and columns of the worksheet.  A one dimensional array can either be one column or one row.

Arrays Cont.  A two dimensional array must have both rows and columns.  An example of a one dimensional row array:  {1,2,3,4,5}  Put this in a cell with an equal sign at the beginning, highlight 5 cells in a single row, press F2 and then CTRL-Shift-Enter

Arrays Cont.  An example of a one dimensional column array:  {1;2;3;4;5}  An example of a 3x2 two dimensional array:  {1,2;3,4;5,6}

Single-Cell Array Formulas  Single-cell array formulas  These formulas give a result in one cell, e.g., ={Sum(A1:A4*B1:B4)}.  When entering an array formula, you must activate the cell and press Ctrl+Shift+Enter

Single-Cell Array Formulas Cont.  Suppose you have the names Bob, Sean, and Stuart in cells A1:A3  If we want to calculate the average length of individuals’ names, we can do it in a single formula using the idea of an array  =AVERAGE(LEN(A1:A3))

Multi-Cell Array Formulas  Multi-cell array formulas  These formulas give a result that spans multiple cells.  In these formulas, you need to select the cells for where the results will be and press F2 to select the cells.

Transposing an Array  A useful array formula is the Transpose function.  This function will take a column array and make it a row array, a row array into a column array, and it will transpose a matrix array.

Frequency Function  The frequency() function calculates the number of times a value occurs in an array, i.e., it helps you create a histogram.  It has two main arguments:  The data_array argument is the array of values your interested in  The Bins_array is the array that has the numbers to be tallied.

Linest Function  The Linest() function returns the results of doing a linear regression on a column array of known Y’s regressed against an array of known X’s.  Linear regression is based on the concept Y = mx + b

Linest Function Cont.  There are four arguments to the function:  Known_y’s – this is the set of numbers for the dependent variable  Known_x’s – this is the set of numbers for the independent variable(s)  Const – If you set this to True, it will estimate a nonzero intercept b; false implies set b to zero  Stats – True gives you a set of regression statistics, while false returns no statistics

Matrix Functions  Excel has three useful matrix functions:  Mmult() which does matrix multiplication of two arrays  Mdeterm() which gives you the determinant of a square matrix  Minverse() which gives the inverse of a square matrix

Matrix Functions Cont.  The functions can be useful when doing matrix algebra, i.e., solving a set of linear equations, but they can have rounding issues  For example:  x+y= 80  x-y=20