how to make an itteration?

N

nienevrouw

Hello!

For my thesis I have made a program to calculate thermal comfort. Fo
this I need the clothing temperature. To calculate this value, I hav
to make an itteration. How can I make this in excel?

The formula is (this is an easier form):

x=5-6*(((x+273)^4)-12)-8*(x-4)

I hope you can help me.

Thanks!!!

regards Nin
 
A

Alex Delamain

There is probably a simpler way but try this:

In cell A1 enter 1
Then Insert Name Define cell A1 as "xvalue"

Enter the formula for X into cell B1 (i
=5-6*(((xvalue+273)^4)-12)-8*(xvalue-4)

Then in cell C1 enter A1-B1

Finally use Tools, Goal Seek
Set Cell C1
To value 0
By changing cell A1

For this equation the result comes out as -268.47 which seems a littl
cold
 
N

nienevrouw

thanks for your reply, but I don't get it...how do I insert the formul
then? With the suggestion you gave me, nothing was changed..
 
N

nienevrouw

thanks alex, I think this will work!!!

Pretty cold indeed :) but the formula wasn't correct, i gave simpl
values
 
D

Dana DeLouis

Hello. Just for discussion. I may be wrong, but with "Iteration", I
usually think of a function that converges. I think that is what Bob was
trying to show. The other option was setting your equation to zero and
solving for x.
Your equation is really just a 4-degree polynomial. It expands to -Infinity
with a starting value of 1. If Solving for zeros, then there are 4
solutions. (2 Real, 2 Complex)

One solution was already given:
-268.595649420017

The other is:
-277.438452775491

I am not exactly sure which you are trying to solve for.
Again, this is just for discussion.

HTH
Dana DeLouis
 
N

nienevrouw

I'm not sure..You have 4 answers thats true..If you program this
iteration in matlab, the the first answer is the correct one..maybe
excel takes the first one aswell...
But I don't know why those programs take the first one..

Does anybody know how you can use the way Alex said, for a whole
dataset? Copy the formula doesn't work (its a single cell value or
so..)
 
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