Substraction of next amount from previous amount.

Freaky · 2009-02-13

Hi Guys, can anyone help me on how I can get the differences between amounts.For example I have a variable called
amount
56
86

so i will like to have an answer of 86-56=30.

Thanks in advance.

jversusj · 2009-02-13

perhaps try giving your variable dimensions and make an array - then you'd have to add code to move the value of amount[1] to amount [2] on each iteration and then you could subtract [1] from [2]... does that get you started?

Freaky · 2009-03-05

Jversusj thanks for the help but I have no idea on how to use arrays in Nav. And my values on the variable "amount" is not just two they are numerous. Can you please assist more.

DenSter · 2009-03-05

MyAmount := 86 - 56;
MESSAGE('The amount is ' + FORMAT(MyAmount));

Freaky · 2009-03-06

Am Sorry if I did not give you a clear picture of what I meant this is how it is

Amount(decimal)
56.00
86.00
86.00
357.00
389.00
413.00
480.00
it continues

Results
0
86-56
86-86
357-86
389-357
413-357
480-413
it continues

So in each case I want to subtract the first value from the second value.

Thanks.

jversusj · 2009-03-06

i think you can do this, like i said, with an array.

create your variable and look at the properties. Set the dimensions property to 2 - this will let you keep 2 values in the variable at a time: variable[1] and varibable [2]. then you would do your processing. on your first record (you could be clever to code for the first time it happens versus all subsequent times), you would set variable[2] = your value. variable[1] would be 0. you could then do variable[2] - variable[1].

for all subsequent records you would first say variable[1] := variable[2], then you would set variable[2] equal your new value. you could then do variable[2] - variable[1] as before and get the difference.

so, using your example values:
56.00
86.00
86.00
357.00
389.00
413.00
480.00
etc.

the first time through, set variable[2] := 56.00. there is no previous entry because you just started, so difference := variable[2] - variable[1] would be 56.00. you could code a different formula if you really want the answer to be 0 (according to your example).
the next record would set variable[1] := 56.00 and variable[2] := 86.00, then difference := variable[2] - variable[1].

you would continue this through all records and always subtract the current from the previous.

MBerger · 2009-03-06

If it's on a form, then you could do the following :
- Add a Global Variable for your difference ( I'l call it Difference )
- Add a textbox to your tablebox, and add the Difference variable as its SourceExpression
- In the OnAfterGetRecord of the form, declare a variable of the same type as the main record ( let's call it PrevRec )

Prevrec.copy(rec) ;
if PrevRec.next(-1) <> 0 then
  //No previous Record found, assume 0 as previous value
  PrevRec.init ;

Difference := Rec.Value - Prevrec.value ;

Oh, and do consider that this will look strange if the records aren't sorted on the value you want to use, and filters might do strange things.

Belias · 2009-03-06

boolfirst := true
repeat
  actualvalue = tb.amount
  if BOOLfirst then begin
    BOOLfirst := false;
    result := 0;
  end else begin
    result := actualvalue - previousvalue;
  end;
  previousvalue := tb.amount;
until tb.next = 0;

***Not tested but should work

Freaky · 2009-03-06

Thanks guys for the help. I finally succeeded by using the array method jversusj posted.

jversusj · 2009-03-06

good to hear, although you should note that belias' code does the same thing, without messing with arrays. you would just set up two variables instead of 1 variable with multiple dimensions.

Belias · 2009-03-06

jversusj wrote:

good to hear, although you should note that belias' code does the same thing, without messing with arrays. you would just set up two variables instead of 1 variable with multiple dimensions.

but at least he learnt arrays...which is good!

Freaky · 2009-03-06

Belias I try using your code and when I try compiling it, it says THERE IS A SYNTAX ERROR.

Thanks

Belias · 2009-03-06

Freaky wrote:

Belias I try using your code and when I try compiling it, it says THERE IS A SYNTAX ERROR.

Thanks

Come on! don't blame me so much!

(joking)...i forgot a semicolon...hmmm 2 semicolon, 1st and 3rd line...i didn't compile the code pefore posting it... 8)
....and put a findset or find('-') before the repeat :whistle:

Freaky · 2009-03-06

Thanks once more.

Substraction of next amount from previous amount.

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