Maths / graph puzzle

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Nick - 23 Oct 2006 10:59 GMT

Hi,

I'm sure I'm being dumb but I can't think of a way to solve this. Any
help appreciated.

Given three given values of "Start", "End" and "Length", I need a
function for variables time "T" and values "X" where at T = 1 X=Start
and at T=Length X=End. However if you graph T and X (T along the Y axis
and X along the X axis) I'd like the graph to look something like the
graph of 1/X, i.e. an exponential like "fade" from Start to End over T
periods.

Hope this makes sense - any ideas appreciated!

Nick

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Mangesh Yadav - 23 Oct 2006 11:21 GMT

probably,

X = (T - 1)/(Length - 1) * (End - Start) + Start

for different values between T = 1 to Length, use the above formula, and
then plot the reqd graph.

Mangesh

> Hi,
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> Nick

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Nick - 25 Oct 2006 13:15 GMT

Hi,

Thanks for the reply. Worked out this formula for a straight line
decrease. What I really am looking for is a way of making the decrease
not a straight line - i.e. a gradual fade, where in the last year the
decrease is far greater than in the first (and also a way of reversing
it so that the decrease in the last year is much less than the decrease
in the first).

Any more ideas?

Nick

> probably,
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> > Nick

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Tushar Mehta - 25 Oct 2006 03:34 GMT

Assuming that your data are such that they will result in the kind of
chart you want...

Plot the T and X data in a XY Scatter chart. Then, double-click the y-
axis. In the resulting dialog box, select the Scale tab. In there
check the options for 'Values in reverse order' and 'Value (X) axis
crosses at maximum value'

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Tushar Mehta
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> Hi,
>
[quoted text clipped - 11 lines]
>
> Nick

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