Excel Grade Mapper

For teachers with a need to convert exam points to grades in Excel.
Maps your grading system into an Excel-function, which will be
copy-pasted into an Excel sheet.
Optionally, you can obtain the grades.
USAGE:
excelfun = excel_grade(grtab)
excelfun = excel_grade(grtab,mycell)
excelfun = excel_grade(grtab,mycell,failgr)
[excelfun,grades] = excel_grade(grtab,points)
grades = excel_grade(grtab,points)
[...] = excel_grade(grtab,mycell,points)
[...] = excel_grade(grtab,mycell,failgr,points)
[...] = excel_grade(grtab,mycell,failgr,points,delta)
INPUTS:
grtab: A matrix: Numerical or a cell-object.
The grading system as a table.
An N-by-2 matrix containing each grade and the corresponding
minimum points. A numerical example:
grtab=[1 6;2 8.5; 3 10;4 11;5 11.5];
- the grade is 1 for minimum 6 points
- the grade is 2 for minimum 8.5 points
- and so on, until best grade is 5 for minimum 11.5 points
- Less than 6 points is failed
- Max points are not given (it was 12 in this example)
You may replace some points by nan (not a number) to perform
numerical interpolation. If so, the minimum and maximum points
have to be included, e.g. grtab=[1 6;2 nan; 3 nan;4 nan;5 11.5]
Alternately, grtab can be a cell-object, which enables grades
as a string: grtab={'D-',6;'D',8.5;'C',10;'B',11;'A',11.5}
A cell object has to be a full grading table (no interpolation)
(Optional inputs)
mycell: A string. Your Excel cell, where the points begin.
For instance, you will paste the output variable excelfun right
next to 'H4', where H4 contains points for the first student.
Default 'A1'.
failgr: A string. The failing grade, e.g. 'F'. Default is zero ('0').
points: A numerical vector of points, case you want the grades in
MATLAB.
delta: Minimum step for points in case there will be interpolation.
Example: 7.1312 points will be rounded to 7.25 if delta=0.25.
Default: delta=0.25.
You need to match delta with your grading system even if there
is no interpolation: delta is used to calculate precision in
your excel function.

OUTPUTS:
excelfun: The excel function that maps points to grades.
grades : The grades that correspond to points. If points are provided
and if there is only one output variable, the output will be
grades.