Excel Determine y=mx+b without graph

I learned how to create a graph and have Excel create y=mx+b. Is there a way to do this  without a graph. I have a lot of data sets where one or two data points are missing and I just need the m value. If I had the slope value, I can then solve for the missing value.

Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

kgerbChief EngineerCommented:
I'm not sure what you're asking.  If you have two points you can figure out the slope between them like this.

m = (y2 - y1)/(x2 - x1)

Is this what you're looking for?

u002dagAuthor Commented:
Thanks for getting back to me so quickly.
For x values, 1, 2, 3, 4, 5, Here are some y values listed horizontally in Excel:
blank cell

I draw the graph and get y=0.331x+45.502
equation is created whether or not there is a blank cell

That works. But I have a lot of similar simple data sets and I don't want to create a dozens of these little graphs just so I can create an equation and then I can manually fill in the value in the blank cell. The blank cell could be in any one or two of the locations.

I hope that helps.

Thanks, Dennis
kgerbChief EngineerCommented:
Ok, I think this will get you where you want to be.

What you're looking for is a least squares linear regression.  This can be done manually using Excels LINEST function.  Look at the example workbook for an example using your data.  One caveat is that it doesn't like blanks.  So, before you can us the formula you need to do a linear interpolation to fill in the empty cells.  If you empty cell is D2 and you want to linearly interpolate between cells C2 and E2 you would use the following formula.

D2 = (C2+E2)/2

This needs to be done for each blank cell in your data.  Then you will be able to use the LINEST formula.  LINEST is an array formula so it must be confirmed using Ctrl+Shift+Enter.  To recreate the example worksheet follow these steps.

1.  Enter the linear interpolation into cell D2
2.  Select the range C5:D5
3.  Type the following:  =LINEST(B2:F2,B1:F1)
4.  Confirm with Ctrl+Shift+Enter

C5 will not contain the slope of the regression line and D5 will contain the y-intercept.  If you have questions or get stuck let me know.


Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Determine the Perfect Price for Your IT Services

Do you wonder if your IT business is truly profitable or if you should raise your prices? Learn how to calculate your overhead burden with our free interactive tool and use it to determine the right price for your IT services. Download your free eBook now!

u002dagAuthor Commented:
u002dagAuthor Commented:
Hi Kyle,
Are you still there?
I got the slope in the first cell.
I can't get the x-intercept in the adjacent cell.
Do I have to push the F2 key somehow? Is there a specific sequence of keys?

Could you please describe the exact sequence of keys you hit.

1.  Enter the linear interpolation into cell D2
2.  Select the range C5:D5
3.  Type the following:  =LINEST(B2:F2,B1:F1)
4.  Confirm with Ctrl+Shift+Enter
kgerbChief EngineerCommented:
No, there is no need to press F2 at any time to get this to work.  Here are some more detailed instructions.
Make sure in step 2 you have both cells selected but C5 should be the active cell.  For example if you select both cells and press tab you will be able to toggle the active cell back and forth.  Make sure C5 is active.
Then, with both cells selected, press the equals sign "=" and enter the formula LINEST( with a beginning parentheses.
Select the known_y's for the first argument, and the known_x's for the second argument (B2:F2 and B1:F1 respectively in our current example).
The final two arguments are optional and can be ignored in this instance.
Add a closing parentheses ")" and confirm the formula by pressing Ctrl+Shift+Enter.

That should do it.  Let me know how you make out.

u002dagAuthor Commented:
Ok, it's working well. Thanks for following up and helping me. Dennis
kgerbChief EngineerCommented:
You're welcome.  Glad to help.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Microsoft Excel

From novice to tech pro — start learning today.