I have this data:
x y
310 516
320 526
325 535
330 587
335 640
340 715
345 857
350 1040
When I perform a third degree polynomial curve fit I get this equation:
y = 0.0106x3 - 10.0266x2 + 3152.3381x - 329943.8370
R2 = 0.9987
Which isnt right. On a calculator, I get negative numbers. Does excel have problems with 3rd degree polynomials?
i have a function in a cell (that works) to extract coefficients from a range of cells in a workbook:
VB: =INDEX(LINEST(CP25:CP27,CQ25:CQ27^{1,2}),1)}
i have variables for cp25:cp27 and cq25:cq27 already defined in my vba code. the values for these in the case i am working on are as follows (returns 110.5):
cp25 = 560
cp26 = 570
cp27 = 580
cq25 = .414
cq26 = .479
cq27 = .536
1) how to do this function in VBA only - this is part of a UDF and cannot have any helper cells
2) how to refer to 560,570,580 as a 'range'. is there a way to put these six variables into my ranges for later processing?
All of the google searches i have deal only with linear regression, taking from existing graphs, or say to just use the function i have above.
I have tried
VB:
Var = Application.WorksheetFunction.LinEst(Sheets("references").Range("CP25:CP27"), Sheets("references").Range("CQ25:CQ27^{1,2}"), 1)
[COLOR=#333333][/COLOR]
but return #value! errors. when i remove the ^{1,2} portion, i do return a value but it is incorrect (returns 160), what is the correct syntax for adding in the ^{1,2}? if you do that would be fantastic, but brings me back to issue #2 in that i need to refer to my variables in the vba code and not this range (as they will eventually be going away).
I have quite a number of 4th degree polynomials and attempting to extract the variables from every equation. I used the formula below (from another thread);
=LOOKUP(99^99,--("0"&MID(A1,MIN(SEARCH({0,1,2,3,4,5,6,7,8,9},A1&"0 123456789")),ROW($1:$10000))))
but it only extracts the first variable.
4th degree polynomial function: f(x) = ax^4 + bx^3 + cx^2 + dx + e
Example of one of the equations: Y = -42.4276 + 319.989 X - 809.094 X^2 + 942.247 X ^3 - 397.587 X^4
I'll like to have the final result like below (Based on the Example equation above)
edcba-42.4276319.989-809.094942.247-397.587
I'm logging temperatures and I want to add the degree symbol "°" to the end of the numbers, how do I do that? It's easy if I just use one number (#°), but how do I do it when adding the lowest and highest in the same cell, e.g. 33-35?
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It looks like this:
Its the degree symbol, however using that symbol in VBA has proved to fail me. I have a large data set that is created for import but it will continue to fail until I remove this, Find(Replace) should work right? But using a search in VBA it deletes the entire cell.
I have a columb of positions which at the moment have a decimal place, I want to substitute the first decimal with a degree ie. S27.01.050 for S27°01.050 This has to apply to all cells in that columb.
View 9 Replies View RelatedI have plotted a graph which compares the miles done with the petrol used.
I'm trying find a formula which allows me to apply the petrol and would give me the miles covered.
From excel I have applied the tread line of polynomial and obtained the following formula...
y = 1E-06x5 - 0.0002x4 + 0.0161x3 - 0.4893x2 + 7.5295x - 20.87
Rē = 0.9989
When is it applied to excel with the value of petrol it does not give me the miles.
I'm working out the formula in a incorrect manner?
I have attached the excel file.
y = 1.083333333x4 - 7.3333333x3 + 16.416667x2 - 6.16667x + 4
Above is the polynomial equation of a trend line as shown on my chart, I have extracted the numbers into separate cells using LINEST, so now I have in cells A20 to E20 the numbers 1.083333333, -7.333333, 16.416667, -6.16667 and 4 respectively.With a "y" value of 25 how do I go about solving for a value of "x".
I've been stubbornly struggling with this on and off for a couple of weeks now and I'm not getting any closer to working it out and the websites I've found explaining the procedure all seem to go over my head by the time I get into the fourth or fifth paragraph.
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I am looking for a function [or method] to calculate a polynomial curve fit. I can do it on a graph with the existing graph and chart tools, but I need to calculate it myself. Does such software exist somewhere in my Excel 2007 package, or can anyone recommend a freeware program? I am hesitant to download an unknown, un-recommended add-in.
The functions of trend lines in charts are nice, but the coefficients of the output equations are all with only one-digit for the polynomial fits. The single-digit fits by the fitting equations often result in higher deviations from what we have seen in the charts.
I also tried to use the statistical functions but it seams that I cannot get any outputs of these coefficients except for the slope of LINEST, which is not sufficient for polynomials.
I also use addins such as as regressions but cannot get anything either to help for these coefficients.
May someone tell me how to make such outputs with more digits so the equations can be more precisely fitting please?
I don't actually own Excel as yet - but I'm wondering if someone could tell me whether Excel is capable of solving what I'm told are 'polynomial equations'. An example of the sort of equation I hope to solve is: d/(1.18 + d) + d/(1.86 + d) + d/(9 + d) + d/(8.8 + d) = 2
d=? {I happen to know d = 3.65(approx) in this example btw}
Often there will be many more than four terms...
=IF(H29=>70,"1st",IF(H29>=60AND>=69,"2:1",IF(H29>=50AND>=59,"2:2",IF(H29>=40AND<=49,"3rd"))))
The formula is to work out the class of an honours degree for a certain student.
I'm familiar with 2d graphs, trendlines, and regression equations. Now I have some tabular data that has 2 input variables and a result. As with my 2d data, I would like Excel to create a polynomial equation of z from the x and y inputs. Can Excel do this, or do I need a plug-in or another software package?
View 12 Replies View RelatedI am trying to do multivariate polynomial regression in excel, trying to correlate data of the form y=f(x1,x2) with second order polynomials:
Y = c + a1*x1 + a2*x1^2 + a3^x1^3 + b1*x2 + b2*x2^2 + b3*x2^3
Using the following command, I have achieved this:
=LINEST(A2:A10,B2:B10^{1,2,3,0,0,0}*C2:C10^{0,0,0, 1,2,3},TRUE,TRUE)
theory Excel uses for this kind of regression?
I have a VBA function that calculates polynomial coefficients for a series of data pairs. One selects the range of cells that the coefficients are to be stored in, and enters the polynomial formula:
{POLFIT(Xa, Ya, N)}
Where Xa is the array of ordinate values, Ya is the array of data values, and N is the polynomial order to be fit.
It is obvious that one needs to select at least N+1 cells when the array funtion is typed in. But, it is easy to select too few cells.
I am looking for a way to test whether enough cells were selected for the range formula: The function declaration is
Function POLFIT(Xa, Ya, N As Integer) As Variant
Various means I have tried to count POLFIT do not return the correct value.
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=IF(A2="","",(INT((LEFT(A2,3)+MID(A2,4,6)/60)*100000)/100000)&"d")
