Polynomial Equations
May 14, 2006
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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Feb 16, 2007
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...
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Feb 9, 2010
I 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
R² = 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.
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Jul 31, 2008
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?
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Sep 7, 2009
For Excel 2007 -
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.
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Nov 21, 2008
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?
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Jan 20, 2014
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?
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Feb 8, 2010
I 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?
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Mar 9, 2007
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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Jul 17, 2014
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).
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Apr 10, 2012
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
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Oct 24, 2013
I am given the function
y = a x + b
And I am supposed to ask the user to enter a value for a and b twice
So I could have 2 equations and solve them
The problem is I am not sure how to solve the 2 equations using VBA?
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Apr 19, 2007
how the Process to solve the following problem:
1A = 15x + 32y + 5z
1B = 6x + 2y + 8z
1C = 3x + 11y + 19z ...
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Feb 17, 2003
I was wondering if the solver was the only way to solve implicit equations. I am looking for something that will automatically solve an implicit equation after the appropriate information is entered into the referenced cells.....
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Dec 12, 2013
I have three different equations i am trying to combine to one line so I do not have to use three columns.
Equation 1.
If recommend quantity is < 100, and the Number of times part number used is one, then Recomnend quantity was used
Ex =IF(F277 100 and the Number of times part number used is greater then one and less then 10, then Recommend quantity was used
Ex =IF(G277100,*and(E277>1),F277*2.0)
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Oct 9, 2007
I am trying to solve a set of simultaneous equations by using SolverOk function in VBA.
I dont want to use the 'SetCell' option so, I wrote the following
SolverOk MaxMinVal:=1, ByChange:= Range("V34:V36")
SolverAdd CellRef:=Range("AK4:AK6"), Relation:=2, FormulaText:="0"
SolverSolve
but I get an internal memory error. However, if I use the solver dialog box directly from excel and not through a macro and keep the 'Set Target Cell' as empty, I get the right solution.
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Mar 30, 2014
I'm trying to find definitions/commands to make excel find the best combinations of several defined scopes and restrictions to make an output number as high as possible.
This is by using a combination of several different equations, maybe excel has a magic trick for all the variables and formulas.
Attached File: forum_heatexchanger.xlsx‎
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Feb 12, 2013
I have a system of 3 equations with 3 unknowns that I would like to solve in Excel.
The equations are
24.792 = A*e^(B/(100-C))
9.857 = A*e^(B/(70-C))
4.590 = A*e^(B/(40-C))
Where e is the exponential function.
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Mar 17, 2014
I have two cells with the following equations:
H3=IFERROR(VLOOKUP(A3&TEXT($A$1,"m/d/yyyy"),'CLABSI_Raw'!$A$1:$M$300,13,FALSE)," ")
I3=IFERROR(VLOOKUP(A3&TEXT($A$1,"m/d/yyyy"),'CLABSI_Raw'!$A$1:$M$300,10,FALSE)," ")
In an adjacent cell, I am trying to use an if statement
J3=if(and(H3<1,I3<1),"yes","no")
I am not getting a return in cell J3.
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Jan 11, 2008
Can excel solve an equation for x with two variables.
Example: 102=125000(X-910)/50000.
I need excel to solve for X
The variables are 102 and 125000
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Nov 6, 2006
is it possible to export a trendline equation from a graph to a cell, or at least to export the coefficients? If yes, how?
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Apr 4, 2014
I am trying to analytically solve an equation to establish a physical value. Unfortunately, it's difficult to do the algebra, so it needs to be done this way.
I have an experimental value for this in "J2", so what I want to do is change F2 to that "I2" is equal to "J2"
Is it possible to get excel to match these values - I have about 200 different cells of this?
The formula is in cell "I2"
=B2*((1-(C2/D2)*((F2/G2)^1.2))^-1.5125)
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Dec 26, 2013
I am about to take a corporate finance course. The textbook uses a ton of basic (complex to me) equations to calculate interest rates, bond premiums, dividend reinvestment scenarios, etc.
I know that Excel has a bunch of specific functions to calculate interest, NPV, etc. but I am NOT interested in using those because I would like to have Excel "do the math" once I enter the formulas (or parts of formulas) correctly.
how to enter the equations below into Excel without using built-in formulas (I'm also not looking to use the Equation editor because I actually to calculate the answers, not just have the visual look/feel of the equation).
1R2 = [(1 + .0194)(1 + .03)]1/2 - 1
If done correctly, 1R2 in the above should equal 2.47%. I am totally fine doing parts of this in separate cells if necessary.
And something more complicated like the below. I wrote out the word "delta" because I don't know how to create the "triangle" symbol for delta on this forum post. According to the text, for securities with semiannual receipt (compounding) of interest, it is represented as:
-D = (delta P / P) / ((delta r sub b) / (1 + (r sub b)/2)))
Or in English, I believe that can be expressed as "negative D equals the quotient of delta P divided by P (in the numerator) divided by the following: delta r sub b divided by the quantity 1 plus r sub b divided by 2"
And finally
V sub b = 1000 / [1 + (.10/2)]2(4) + 50 times the following compound bracketed expression [1 - (1 / [1 + (.10/2)]2(4)] divided by (.10/2)]
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Aug 22, 2009
I need to automate the attached as per the following (by not recording macro unfortunately).
Sheet one has a dump of data. First, I need to change the data format from yyyymmdd to dd/mm/yyyy. Then I need to filter for region EU and only copy the filtered data from columns A, C-D, F and the difference from columns I-J to Sheet 2. Then in Sheet 2, I need another column to calculate the difference per unit.
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Mar 26, 2009
Combining two equations with MOD function for UPC check digit calculation.
I wanted to combine these if possible,
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Aug 6, 2014
Any way to exclude colored cells from addition in a column. I will attach a simple example document.
I am building a spreadsheet to keep track of my monthly spending, and debt balance. I keep track of the total amount of bills I pay each month. As I pay them, their respective line is highlighted green in the spreadsheet. I would like to create a macro/formula which would sum the remaining cells in the column which are not highlighted to display the remaining monies which need to be paid out. I'm not sure if this matters but I am using office 2010.
billSample.xlsx‎
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Dec 31, 2013
I had a question about adding numbers, sort of like algebra equations (best description I can think of) into a spread sheet. Example:
Cell A1: 8
Cell A2: 8l
Cell A3: 8ls
Cell A4: 8l
Cell A5: 8
Cell A6: -where I want the total to be displayed in the following way: 16+16l+8l
Is this even possible to calculate by grouping like numbers?
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Jan 13, 2009
I am using the following equation to add together up to eight different sound levels:
=10*LOG(10^H14+10^I14+10^J14+10^K14+10^L14+10^M14+10^N14+10^O14)
It works perfectly, except that due to the nature of the equation, if there are no values entered for any sound levels the answer will be 9. Is there any way to check to see if any values are present? I've been looking into IF functions and I've tried (unsuccessfully):
=IF([=10*LOG(10^H14+10^I14+10^J14+10^K14+10^L14+10^M14+10^N14+10^O14)]=9, 0, [10*LOG(10^H14+10^I14+10^J14+10^K14+10^L14+10^M14+10^N14+10^O14)])
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