Intersection of 2 curves
Solved
MarcD1
Posted messages
5
Status
Membre
-
Raymond PENTIER Posted messages 58546 Registration date Status Contributeur Last intervention -
Raymond PENTIER Posted messages 58546 Registration date Status Contributeur Last intervention -
Hello,
I am looking for an EXCEL sheet that would calculate the intersection between 2 curves (X,Y), even if this intersection is in the extension of the curves (meaning the extensions of the curves would be calculated), and would return the coordinates (X,Y) of the intersection point. There should also be an error message if the 2 curves cannot intersect.
Configuration: Macintosh / Safari 12.0.2
I am looking for an EXCEL sheet that would calculate the intersection between 2 curves (X,Y), even if this intersection is in the extension of the curves (meaning the extensions of the curves would be calculated), and would return the coordinates (X,Y) of the intersection point. There should also be an error message if the 2 curves cannot intersect.
Configuration: Macintosh / Safari 12.0.2
5 réponses
Hello.
Question too general.
Are your curves defined by functions or drawn point by point like successive measurements?
--
Retirement is great! Especially in the Antilles...
Raymond (INSA, AFPA)
Question too general.
Are your curves defined by functions or drawn point by point like successive measurements?
--
Retirement is great! Especially in the Antilles...
Raymond (INSA, AFPA)
MarcD1
Posted messages
5
Status
Membre
They are curves drawn point by point, like for successive measurements.
So, to be very clear:
- if the curve is defined by points, as you confirm in post #2, there is only the method I indicated to you.
- if the curves are representative of algebraic functions, the calculation is straightforward by writing y1=y2 and finding the value of x that satisfies this equality, even if the intersection is outside the bounds of the graph; we can also display "no intersection" if the curves are parallel or diverging.
--
Retirement is great! Especially in the Caribbean...
Raymond (INSA, AFPA)
- if the curve is defined by points, as you confirm in post #2, there is only the method I indicated to you.
- if the curves are representative of algebraic functions, the calculation is straightforward by writing y1=y2 and finding the value of x that satisfies this equality, even if the intersection is outside the bounds of the graph; we can also display "no intersection" if the curves are parallel or diverging.
--
Retirement is great! Especially in the Caribbean...
Raymond (INSA, AFPA)
Thank you for the response. But it's not that simple, the two curves do not have the same values of X, which means that for (X1,Y1) & (X2,Y2), X1 > < X2 and Y1 > < Y2, and moreover, we are not sure that the intersection, if it exists, is within the measured data range for each of the curves (X1,Y1) and (X2,Y2), hence my question. Of course, we can simulate each curve with an equation and vary X1 = X2 with these 2 equations and proceed as you described, but if the 2 curves do not intersect we will have a random result, hence a second difficulty if I want to automate the EXCEL sheet.
I did my best with the few pieces of information provided.
Working without the relevant file is inherently random.
Working without the relevant file is inherently random.
1) Go to https://www.cjoint.com/
2) Click on [Browse] to select your file (max 15 MB)
3) Scroll down to click on the blue button [Create Cjoint link]
4) After a few seconds, the second page will display, with the link in bold; right-click on it and choose "Copy link"
5) Go back to your discussion on CCM, and in your message, do "Paste".
=>See the guide https://www.commentcamarche.net/faq/29493-utiliser-cjoint-pour-heberger-des-fichiers
So:
- in column A, the x coordinates
- in column B, the y coordinates of the curve y1
- in column C, the y coordinates of the curve y2
- in column D, the difference y2-y1
- in E2, the formula =SIGN(D2)-SIGN(D3)
When column E shows -1, it means we have reached the intersection.
It's nice, retirement! Especially in the Caribbean...
Raymond (INSA, AFPA)
- in column A, the x coordinates
- in column B, the y coordinates of the curve y1
- in column C, the y coordinates of the curve y2
- in column D, the difference y2-y1
- in E2, the formula =SIGN(D2)-SIGN(D3)
When column E shows -1, it means we have reached the intersection.
It's nice, retirement! Especially in the Caribbean...
Raymond (INSA, AFPA)