# Creating a new column

You can calculate new columns based on old ones in Minitab. The LET command in Minitab is used to calculate a column. The syntax is this:

`MTB> LET column= arithmetic expression`

The following example calculates the improvement from TEST1 to TEST4.

`MTB> LET C6=C5-C2`

Since C5 and C2 are named, we could have also done this:

`MTB> NAME C6= 'IMPROV' MTB> LET 'IMPROV'='TEST4' -'TEST1'`

Arithmetic operators include +, -, * (for multiply), / (for divide), and ** (for exponentiation). Also parenthesis can be used to clarify complex operations. The following example calculates column 7 as the square of column 6.

`MTB> LET C7= C6**2`

Rowwise statistical functions can also be used to compute a statistic across a series of columns, and to put the result in the corresponding locations of the new column. The following example computes C8 as the mean of C2 to C5.

`MTB> RMEAN C2-C5 C8`

More complex operations are possible. The following example would compute a weighted mean if the first three tests were worth 50% of the grade and the final test were worth 50% of the grade.

`MTB> LET C8=(.50*((C2+C3+C4)/3))+(.50*C5)`

The following are MINITAB rowwise statistics.

RCOUNT col-col resultcol -- gives the count of values in the row.

RN col-col resultcol -- gives the number of non-missing values across the row.

RNMISS col-col resultcol -- gives the number of missing values across the row.

RSUM col-col resultcol -- gives the sum of the values across the row.

RMEAN col-col resultcol -- gives the mean of the values across the row.

RSTDEV col-col resultcol -- gives the standard deviation of the values across the row.

RMEDIAN col-col resultcol -- gives the median of the values.

RMINIMUM col-col resultcol -- gives the minimum value across the row.

RMAXIMUM col-col resultcol -- gives the maximum value across the row.

RSSQ col-col resultcol -- gives the uncorrected sum of squares.