Date: Nov 21, 2012 7:51 PM
Author: Dr Reinhard Simonovits
Subject: Cannot calculate with Dynamic variables

Hi,

I have a problem with Dynamic variables.

This is a prototype of a grading scheme. In reality it is bigger. The
10 pts in initPtsPartAcome from the school.

The output cell should be deployed as a CDF file for the teacher. The
teacher enters the points of the students and gets a final mark.

I have two questions.

1) How can I limit the InputField to allow for integer numbers between 0
and 10? If I enter anything else, say a negative number or a symbol,
it should be cleared automatically.

2) In "Why don't the calculations work?" you see expressions with
Dynamic variables which I need to work with. What is wrong? What is the
solution?

DynamicModule[ {mark4 = 1/3,
mark3 = 0.51,
mark2 = 0.68,
mark1 = 0.80,
initPtsPartA = {
{10, 8, 10, 6},
{10, 5, 10, 5},
{10, 7, 10, 1}},
initPtsStudent, initPtsSchool, initPtsPartSum, numTable,
SchoolAPts, StudentAPts, StudentMinAchieved
},

numTable[x_, y_ /; OddQ[y]] := initPtsPartA[[x, y]];
numTable[x_, y_ /; EvenQ[y]] :=
InputField[Dynamic@initPtsPartA[[x, y]], Number,
ContinuousAction -> True, FieldSize -> 1];


initPtsPartSum[x_, y_, col_] :=
Dynamic@Total[initPtsPartA[[x ;; y, col]]];


SchoolAPts = (Total[initPtsPartA[[1 ;; 3, #]]] &) /@ {1, 3};
StudentAPts = (initPtsPartSum[1, 3, #] &) /@ {2, 4};


Column[{Grid[
Append[ Array[numTable, {3, 4}], (initPtsPartSum[1, 3, #] &) /@
Range[4]]],

{"Just Testing Values:", initPtsPartSum[1, 3, 1],
initPtsPartSum[1, 3, 2], initPtsPartSum[1, 3, 3],
initPtsPartSum[1, 3, 4], "Student Pts only:", StudentAPts},

{"Why don't the calculations work?",
Dynamic[5*initPtsPartSum[1, 3, 2] + 10],
Dynamic[initPtsPartSum[1, 3, 4] > 30],
Dynamic[ Total[(initPtsPartSum[1, 3, #] &) /@ Range[4]] ],
Dynamic[(Total@StudentAPts)]/(Total@SchoolAPts)},

{"Why don't the calculations work?",
StudentMinAchieved =
Dynamic[(StudentAPts[[1]]/SchoolAPts[[1]] >
mark4) && (StudentAPts[[2]]/SchoolAPts[[2]] > mark4)]}

}]

]


Liebe Grüße, Best wishes, Reinhard

--
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Dr. Reinhard Simonovits
Handelsakademie | Karl Franzens University
Math Department | Inst. for Mathematics
Grazbachgasse 71 | Heinrichstrasse 36
A-8010 Graz, Austria

Email: Reinhard.Simonovits@uni-graz.at
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