Hi, I will try to explain what it is I need to do, how far I am in doing it yet and where my problem is:
I have a lot of x,y values I need to fit a non linear function through. Subsequently, I need to find the intersection point of this fitted curve with y=1.01 The problem is I have a lot of values so I want to be able to do it all at once. I already imported my excel file of the points I have to use. The things I already have are following (not all of the data is visible because otherwise the file would be too long for this email, but i just showed part of my data so you could better understand my problem): ______________ X1242 X1242.5 X1243 X1243.5 X1244 X1244.5 X1245 X1245.5 X1246 X1246.5 X1247 X1247.5 X1248 X1248.5 X1249 => names of each data set ( corresponds to wavelengths, ranges from 400 to 2500 with 0.5 steps => a lot of points!) 18.14 0.9860316 0.9860272 0.9860203 0.9860121 0.9860044 0.9859994 0.9859971 0.9859976 0.9859999 0.9860035 0.9860069 0.9860103 0.9860128 0.9860151 0.9860178 15.8 0.9857134 0.9857106 0.9857063 0.9857011 0.9856958 0.9856917 0.9856887 0.9856874 0.9856880 0.9856893 0.9856906 0.9856919 0.9856922 0.9856916 0.9856912 13.77 0.9930109 0.9930015 0.9929921 0.9929833 0.9929765 0.9929714 0.9929674 0.9929637 0.9929603 0.9929569 0.9929533 0.9929501 0.9929469 0.9929440 0.9929416 9.03 0.9875374 0.9875321 0.9875242 0.9875140 0.9875024 0.9874921 0.9874840 0.9874793 0.9874780 0.9874802 0.9874835 0.9874869 0.9874877 0.9874857 0.9874801 6.14 0.9900554 0.9900465 0.9900376 0.9900286 0.9900204 0.9900122 0.9900032 0.9899924 0.9899802 0.9899669 0.9899544 0.9899445 0.9899372 0.9899333 0.9899317 4.27 1.0050327 1.0050242 1.0050175 1.0050129 1.0050107 1.0050101 1.0050094 1.0050070 1.0050025 1.0049959 1.0049885 1.0049812 1.0049746 1.0049691 1.0049647 2.77 0.9892697 0.9892585 0.9892454 0.9892311 0.9892164 0.9892030 0.9891906 0.9891796 0.9891704 0.9891624 0.9891550 0.9891480 0.9891401 0.9891320 0.9891235 1.52 0.9979284 0.9979430 0.9979548 0.9979644 0.9979739 0.9979850 0.9979984 0.9980137 0.9980312 0.9980498 0.9980691 0.9980897 0.9981105 0.9981323 0.9981542 These are my x-values and y-values X1249.5 X1250 X1250.5 X1251 X1251.5 X1252 X1252.5 X1253 X1253.5 X1254 X1254.5 X1255 X1255.5 X1256 X1256.5 18.14 0.9860214 0.9860261 0.9860320 0.9860377 0.9860425 0.9860456 0.9860462 0.9860449 0.9860433 0.9860422 0.9860417 0.9860428 0.9860444 0.9860456 0.9860456 15.8 0.9856911 0.9856918 0.9856934 0.9856958 0.9856984 0.9857014 0.9857040 0.9857069 0.9857099 0.9857132 0.9857153 0.9857156 0.9857132 0.9857080 0.9857016 13.77 0.9929406 0.9929405 0.9929425 0.9929445 0.9929464 0.9929476 0.9929476 0.9929455 0.9929431 0.9929409 0.9929377 0.9929356 0.9929331 0.9929304 0.9929279 9.03 0.9874721 0.9874641 0.9874578 0.9874542 0.9874529 0.9874541 0.9874556 0.9874563 0.9874565 0.9874551 0.9874527 0.9874498 0.9874461 0.9874415 0.9874371 6.14 0.9899318 0.9899319 0.9899304 0.9899263 0.9899192 0.9899095 0.9898986 0.9898873 0.9898777 0.9898703 0.9898641 0.9898591 0.9898546 0.9898495 0.9898439 4.27 1.0049605 1.0049564 1.0049528 1.0049495 1.0049466 1.0049435 1.0049404 1.0049357 1.0049298 1.0049230 1.0049155 1.0049093 1.0049049 1.0049019 1.0049002 2.77 0.9891158 0.9891100 0.9891058 0.9891036 0.9891013 0.9890986 0.9890943 0.9890873 0.9890789 0.9890691 0.9890583 0.9890485 0.9890395 0.9890323 0.9890266 1.52 0.9981760 0.9981970 0.9982176 0.9982372 0.9982565 0.9982753 0.9982935 0.9983102 0.9983259 0.9983408 0.9983533 0.9983647 0.9983749 0.9983841 0.9983929 X1257 X1257.5 X1258 X1258.5 X1259 X1259.5 X1260 X1260.5 X1261 X1261.5 X1262 X1262.5 X1263 X1263.5 X1264 18.14 0.9860445 0.9860437 0.9860438 0.9860467 0.9860527 0.9860613 0.9860705 0.9860782 0.9860830 0.9860844 0.9860832 0.9860806 0.9860774 0.9860746 0.9860716 15.8 0.9856955 0.9856925 0.9856930 0.9856967 0.9857032 0.9857098 0.9857162 0.9857213 0.9857248 0.9857268 0.9857283 0.9857298 0.9857314 0.9857340 0.9857374 13.77 0.9929253 0.9929242 0.9929234 0.9929239 0.9929254 0.9929276 0.9929302 0.9929321 0.9929329 0.9929328 0.9929315 0.9929294 0.9929275 0.9929257 0.9929243 9.03 0.9874330 0.9874313 0.9874312 0.9874335 0.9874375 0.9874418 0.9874468 0.9874510 0.9874547 0.9874577 0.9874602 0.9874623 0.9874640 0.9874659 0.9874680 6.14 0.9898392 0.9898366 0.9898360 0.9898381 0.9898417 0.9898455 0.9898484 0.9898489 0.9898469 0.9898432 0.9898392 0.9898363 0.9898354 0.9898371 0.9898402 4.27 1.0048982 1.0048966 1.0048942 1.0048923 1.0048914 1.0048917 1.0048929 1.0048939 1.0048933 1.0048910 1.0048865 1.0048803 1.0048742 1.0048693 1.0048658 2.77 0.9890227 0.9890210 0.9890197 0.9890184 0.9890164 0.9890143 0.9890120 0.9890102 0.9890088 0.9890087 0.9890089 0.9890086 0.9890073 0.9890056 0.9890024 1.52 0.9984034 0.9984168 0.9984328 0.9984514 0.9984707 0.9984899 0.9985069 0.9985223 0.9985357 0.9985479 0.9985593 0.9985694 0.9985778 0.9985845 0.9985890 %% I tried: > test1<-nls(y~I(1+a*exp(1)^(-b*x)),data=model,start=list(a=1,b=1)) Warning messages: 1: In min(x) : no non-missing arguments to min; returning Inf 2: In max(x) : no non-missing arguments to max; returning -Inf > test1 Nonlinear regression model model: y ~ I(1 + a * exp(1)^(-b * x)) data: model a b 12.58 2.66 residual sum-of-squares: 0.0005495 Number of iterations to convergence: 12 Achieved convergence tolerance: 8.038e-06 > Now I first tried it with a small data set of only 1 set of x and y values, and found that the formula I use works so that's ok. But now the objective is to perform the formula to the total data set and get an overview of the a and b values *for each other data set (so for each wavelength), not an average a and b value for everything*. Is this possible? How do I do it? _______________________________________________________________ Secondly, for the intersection point determination, I found on the internet to use the function >intersection(sequenceInd = NA, sequenceSig = NA, hLine = NA, plot = TRUE) but when I do this, the response I get is > intersection(sequenceInd=model,hLine=1.01,plot=TRUE) Error: could not find function "intersection" The intersection line is the same for each data set. How can I find the intersection point for each dataset? _______________________________________________________________ Thank you so much in advance, Karen Vandepoel -- Karen [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.