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On 2013-02-18 07:31, Hylton Conacher (ZR1HPC) wrote:
Hi Tom,

On 14/02/13 16:41, Tom wrote:
Hi :)
Yes, of course you can ask different questions.  I just thought it was
exactly the same question again in which case my answer wouldn't have been
so wrong.

Thanks , I was hoping so.


I wonder if there is a really good Maths forum for getting help with this sort of thing. It's a bit sideways from our normal ways of thinking so we might not be much good at it. A Maths forum like that might even be good place for students or kids to get unusual but real-life questions to figure out. A chance for teachers to escape irrelevant ancient dusty text-books
and get real.

Whilst I agree a good Maths/Calc forum wouldn't be a bad idea, I think considering the software in use on LibreOffice Calc, then the users should mostly be able to find a resolution to their problem regarding formula syntax and entry. This problem is complex but hopefully once solved will help others with scale calculations.

Given the subscribers to the list are the folk who would be most likely to use the formula, its correct usage and syntax is imperative or perhaps it might indicate a problem with a formula in Calc's repertoire.

Of course an obvious answer is to avoid using a spreadsheet for this
initially and just use the back of an envelope or scrap of paper from
elsewhere. When the question states "the amount of unit i have left" that
suggests an upper limit that can't be exceeded such that
Total amount of units allowed = Used + amount left
So i think i need to know which of these 2 following statements are true and
which isn't (or am i completely off-track?)
G2= Total amount allowed, the limit
G2 = amount left
In the question it seems to be being used in both ways at different times.
Well, to me anyway.
Scraps of paper are sometimes a handy quickie solution but if the results need graphing over a few readings, a spreadsheet really is better as I am sure you'll agree :) , mind you that said a database would be the best, but that gets REALLY complicated. :)

G2 in this example is the total electricity unit reading taken at the end of the month that indicated how many units are left or available. What I am aiming to work out is the currency value of those units(H2) using the same scale that is used to purchase the units.

Using my Purchase scale and changing the purchase value in c22 for e.g., I can see that I would need to layout ZAR574.61 to be allocated 150 units on the first scale and 282.99 on the second scale totalling R574.60,5 - vat= R504.05 to give me the value of 433 units.

The question is to work out the value obtained in c22 auto-magically for H2, without using C22 to give the ZAR value of G2 or 432.9 units.

The formula in H2 incorporates the first two scales i.e. `=IF(G2>=$G$18,$H$18,G2*$F$18)+IF(G2-$G$18>=$J$18,$K$18,(G2-$G$18)*$I$18)' Provided G2 is 433 the correct answer for H2 of R504.05 is received. HOWEVER using the same formula, if you make G2 =1. The answer in H2 should be R1.13 yet shows an answer of R -174.85?

As the above formula only incorporates 2 of the 3 scales, the full formula is `=IF(G2>=$G$18,$H$18,(G2*$F$18))+IF(G2-$G$18)>=$J$18,$K$18,(G2-$G$18)*$I$18)+IF(G2-$G$18-$J$18)>=$M$18,$N$18+(G2-$G$18-$J$18-$M$18)*$L$19,(G2-$G$18-$J$18-$M$18)*$L$19)' yet for some reason I am getting a 508 error yet I have checked the number of brackets and all is OK?

zr1hpc wrote
Using Calc 3.4.5 on openSuse 11.2

I am trying to work out the currency value of the amount of electricity
units I have left at the end of the month (G2).

This same formula will be used for the other 11 months of the year with
only the G2 reference changing to G3, G4...etc.
For those who wish to stretch their grey matter as mine just ain't
stretching any more.

The pricing scale the energy supplier has given me is:

Unit Range        Value per unit
0-150            1.1320
150.01 -> 600    1.1811
600.01 ->        1.4018

Therefore the first 150 units are priced at 1.132 ea. any units still
available need to be calculated at the next rate of 1.1811, but only up to
449.90 units at the second rate. Anything more than that must be at the
highest rate of 1.4018.

Assuming my unit balance of G2 = 433 I can work out the currency value of
G2 by following the following logic, and using the scale above:

433 > 150 therefore the initial 150 units need to be priced at 1.1320 i.e. 150* 1.132= ZAR169.80. To this the balance of the units over 150 need to be multiplied by the next rate of 1.1811 i.e. 433-150= 283. Since 283 is below the max of 449.9 units allowed for this scale, therefore 283*1.1811=
ZAR334.25. The third scale is not needed as all the units have been
accounted for, however it must be available should G2 exceed 600 units
e.g. taking 601 units; the first 150 would be costed at 1.132, the next
449.9 costed at 1.1811 and the balance of 1.1 units costed at 1.4018 per

Therefore total value of 433 units is:
   150*1.1320 = 169.80
+ 283*1.1811 = 334.25
Value        ZAR504.05

Values used in formulae below are:
G2 = 433 available units
$F$18 = 1.132 cost per unit
$G$18 = 0 -> 150 units
$H$18 = 169.80 = value of F*G
$I$18 = 1.1811 cost per unit
$J$18 = 150.1 -> 600 units
$K$18 = 531.38 = value of I*449.90 = 600-150.1
$L$18 = 1.4018 cost per unit
$M$18 = 600.01
$N$18 = 841.09 = M*L however this value is dependent on how many units
         over 600 column G2:g13 is.


Even taking out the SUM(), and replacing 'commaIF' with '+IF's gives the
incorrect answer i.e. 467.22.

There must be a problem with my logic in the above formula as the answer
is so close, but for the life of me I cannot see it.

Asking for some 'logic'al help to work out the correct value in H2:H13

File attached via Nabble:

If you have G2 as your input,
F18 = 1.132, G18=150, H18=1.1811, I18=600, J18=1.4018
 and calculate your answer with

It seems to work ok.
You and cut and paste the formula into the formula bar.
Your organisation on the page may not lead to easy copying down, I don't know if you want to accommodate different tariffs in different months or if the tariffs stay the same. If the tariffs can vary each month then you can get rid of a lot of $ signs to make copying easier.

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