Help - I've even forgotten if I knew this 40 years ago when studying maths
as it's completely Greek to me now.
Just did a 3rd order polynomial curve fit in Excel and got the following equation
y = 13.224x^3 - 79555x^2 + 2E+08x - 1E+11
Now want to calculate some y values but don't know what the "E" is and what it's value is.
There's obviously more to it than meets the eye as +2E-1E = E but they kept them separate, and what's the implication of "08x" -
why not just "8x"?????
E = times ten to the power of
so:
y = 13.224x(to the power of) 3 - 79555x(to the power of) 2 + 2 x 10(to the power of)8x - 1 x 10(to the power of)11
[Edited on 13/10/09 by cd.thomson]
badda, badda, what...?
Doesn't the "E" mean to the power of like on a calculator?
E means Exponential e.g 218400000 = 2.184E08
[Edited on 13/10/09 by omega0684]
quote:
Originally posted by nick205
badda, badda, what...?
Doesn't the "E" mean to the power of like on a calculator?
Ivan
Just change your cells within excel to "number" format and you will see the number displayed in full.
Excel uses E to allow large numbers to be displayed in small cells. Omega0684 is correct
RD 
quote:
Originally posted by Ivan
Just did a 3rd order polynomial curve fit in Excel and got the following equation
y = 13.224x^3 - 79555x^2 + 2E+08x - 1E+11
Now want to calculate some y values but don't know what the "E" is and what it's value is.
quote:
Originally posted by omega0684
E means Exponential e.g 218400000 = 2.184E08
[Edited on 13/10/09 by omega0684]
quote:
Originally posted by Alex.
quote:
Originally posted by omega0684
E means Exponential e.g 218400000 = 2.184E08
[Edited on 13/10/09 by omega0684]
That would be 'e', in lowercase.
Alex.
lower case e would be the mathematical irrational constant
Be careful if you are using the polynomial from an Excel curve fit to actual generate your own data, you may find the generated data has very large
errors.
The problem is the number decimal places that Excel displays by default can be much lower than required. If you right click on the box in your chart
displaying the polynomial, select "Format data labels" and choose the "Number" tab, you can now select "Number" as the
Category and select the number of decimal places to display. You often need a lot of digits to get good data from higher order polynomials.
Thanks guys - tomorrow when I am more alert I will try out your suggestions.
quote:
Originally posted by liam.mccaffrey
lower case e would be the mathematical irrational constant
After thinking about it for a while the normal expression for this type of curve is "y= Ax^3 - Bx^2 + Cx - D" so I would guess that the
equation is most probably "y = 13.224x^3 - 79555x^2 + (2E+08x) - (1E+11)"
Unfortunately that and just about any other combination gives absolutely ridiculous answers in the order of Billions instead of hundreds
For instance where x=2003, y should approx 400 but calculates to 87 700 000 000
y = 13.224x^3 - 79555x^2 + 200000000x - 100000000000
so for X= 2003
Y= 13.224(8036054027)-79555(4012009)+400600000000-100000000000
=106268778453.05-319175375995.00+400600000000.00-100000000000.00
=87693402458.05
Sorry for the horrendous notation but it avoids any potential confusion.
How did you find the equation?
quote:
Originally posted by alistairolsen
How did you find the equation?