What is the equation of the logarithmic line? Different people use different
expression - what do you use?

--
Bernard Liengme
http://people.stfx.ca/bliengme
Microsoft Excel MVP

"Maria F" wrote in message ...
How can I find the intersection between a logarithmic curve and a straight
line?

Thanks.



Bernard Liengme wrote:

I will assume you have two straight lines - if not please tell me what
they
30-Aug-07

I will assume you have two straight lines - if not please tell me what
they
are.

Let the lines follow the two functions
y1=m1x1+b1 and y2=m2x2+b2
Let the point of intersection be Y and X
Then m1X+b1=m2X+b2, giving X=(b2-b1)/(m1-m2)

In Excel terms,
X=(INTERCEPT(y-values2,x-values2)-INTERCEPT(y-values1,x-values1))/(SLOPE(y-values1,x-values1)-SLOPE(y-values2,x-values2))
and Y =SLOPE(y-values1,x-values1)*X+INTERCEPT(y-values1,x-values1)

Put these two formulas in cell A100 and B100
Select A1:B100 and Copy
Click chart; use Edit |Paste Special| specify New Series with X-value in
first cell
Click OK
Now the chart has the point of intersection as a marker.
best wishes
--
Bernard V Liengme
Microsoft Excel MVP
www.stfx.ca/people/bliengme
remove caps from email

"Nana Adwoa" wrote in message
...

Previous Posts In This Thread:

On Thursday, August 30, 2007 2:34 PM
NanaAdwo wrote:

How do i locate the point of intersection of two lines graphs
I have a plot of two lines using excell which intersect at a point. I want
to
locate the point of their intersection using excell and show the
co-ordinates
of that point so that any body can see that i read that point from it.
Step by step procedurewould be helpful and i am using microsoft excel
2007.
Thanks.

On Thursday, August 30, 2007 2:48 PM
Bernard Liengme wrote:

I will assume you have two straight lines - if not please tell me what
they
I will assume you have two straight lines - if not please tell me what
they
are.

Let the lines follow the two functions
y1=m1x1+b1 and y2=m2x2+b2
Let the point of intersection be Y and X
Then m1X+b1=m2X+b2, giving X=(b2-b1)/(m1-m2)

In Excel terms,
X=(INTERCEPT(y-values2,x-values2)-INTERCEPT(y-values1,x-values1))/(SLOPE(y-values1,x-values1)-SLOPE(y-values2,x-values2))
and Y =SLOPE(y-values1,x-values1)*X+INTERCEPT(y-values1,x-values1)

Put these two formulas in cell A100 and B100
Select A1:B100 and Copy
Click chart; use Edit |Paste Special| specify New Series with X-value in
first cell
Click OK
Now the chart has the point of intersection as a marker.
best wishes
--
Bernard V Liengme
Microsoft Excel MVP
www.stfx.ca/people/bliengme
remove caps from email

"Nana Adwoa" wrote in message
...


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