cosinus function in excel not working.

[Fuga]

Ok, so I´m continuing the thread here.

First, I have a reference column, containing values of a rising temperature. This is a straight line in a graph.

My goal is to simulate variances of the temperature, given the straight line. I want to do this by creating "perfect" waves around the line.

I use one cosinus column to simulate an "upward" arch, and another cosinus column to simulate the "downward" arch.

Now the upward arch should begin whenever the downward arch crosses the straight line, and vice versa.

The cosinus functions get their value from another column (well one each of course) where the value of X in cosX starts at a minus value and counting up, thus passing X=0 which is maximum for cosinus function (the downward curve is simply the inversion of this curve).

So to summarize:
Whenever cosinus column A crosses the straight line it sets of cosinus column B (starting at a minus value for X).

The problem is excel is simply calculating wrong. For example the X counting doesn´t start allthough there is an intersection, or it starts regardless of the intersection.

Does anyone have a suggestion?

Fuga.

 

[shades]

Howdy. Not sure I have an answer for you. But it is a little confusing, since you seem to be "continuing a thread" but no background. Is there a connection? Do you have a small sample?
________
SELL VAPORIZERS

 

[neileg]

I think your formula should be:
Y= aX+ bcosX
where a dictates the slope of the graph and b the amplitude of the variation.

Not sure why you need to 'simulate' this formula, can't you just use it the way it is?

 

[Fuga]

Thank you for your answers.

shades - this is the start of the thread.

http://www.access-programmers.co.uk/forums/showthread.php?t=112321


neileg - The reason I´ve done it this way is that I want to determine the number of observations between an intersection and the cosinus function max/min. So that when there is an intersection, the maximum distance between the straight line and the cosinus line will occur after say 20 observation.

Now I´m not at all good att trigonometrics, so maybe you can do it some other way.

Please let me know if you have a better idea.

Fuga.

 

[Fuga]

Neileg-

I finally understood what you meant. I will try it.

The thing is I might want to use this on more irregular curves as well, but maybe it works. I´ll let you know.

Fuga.

 

[Ron_dK]

Fuga,

Just found this with google :

http://www.afpc.tamu.edu/courses/622/files/technical/Simetar 2006 Users Manual.pdf

I realize , it's a lengthy document but it gives some good examples how to set up Excel graphs, lines, etc.

Hope this helps,

Cheers, Ron

 

[Fuga]

Thanks Rak!

Very interesting.

Fuga.

 

[Fuga]

well I´ll be ******.

It turns out I really had a cirkular reference in the workbook. It is now working like it should.

Thanks everyone for your help.

Fuga.