I am having problem running nlme with Logistic model and Four-parameter
Logistic Model. Splus gives me a fitting error. Any recommendations?
Here is Splus output of a simple model:
-----------------------------------
> fit<-nlme(y~SSfpl(logx,A, B, xmid, scal),
+ data=z,
+ fixed=A+ B+ xmid+ scal~1
+ )
Problem in nls(y ~ cbind(1, 1/(1 + exp((xmid - x)/exp(lscal)))), data =
data.frame(xy..: step factor reduced below minimum
Use traceback() to see the call stack
> fit<-nlme(y~SSlogis(logx,Asym, xmid, scal),
+ data=z,
+ fixed=Asym+ xmid+ scal~1
+ )
Problem in nls(y ~ 1/(1 + exp((xmid - x)/scal)), data = xy, start =
list(xmid = aux[1..: step factor reduced below minimum
Use traceback() to see the call stack
--------------------------------
And here is dump of z:
------------------------------------------
"z" <-
structure(.Data = list(c(-6.1508755397365853, -5.9004574713046667,
-5.6500390210702003, -5.3996196291291731, -5.1491994308754458,
-4.8987796212089441,
-4.3979400086720375, -6.1508755397365853, -5.9004574713046667,
-5.6500390210702003, -5.3996196291291731, -5.1491994308754458,
-4.8987796212089441, -4.6483598198914011, -4.3979400086720375,
-6.1508755397365853, -5.9004574713046667, -5.6500390210702003,
-5.3996196291291731, -5.1491994308754458, -4.8987796212089441,
-4.6483598198914011, -4.3979400086720375)
, c("604" = 0.047212741751990896
, "588" = 0.05128205128205128
, "603" = 0.029541689674213143
, "587" = 0.029633933759442184
, "602" = 0.048735511064278189
, "586" = 0.057489123679303915
, "585" = 0.1094941094941095
, "143" = 0.034290738569753815
, "123" = 0.031791907514450865
, "142" = 0.055234239444765756
, "122" = 0.040374488004681103
, "141" = 0.0344336937962436
, "121" = 0.023044269254093388
, "140" = 0.033013205282112844
, "120" = 0.19625137816979052
, "376" = 0.021447721179624665
, "356" = 0.026430348258706465
, "375" = 0.02303894679100384
, "355" = 0.024709302325581398
, "374" = 0.03775811209439528
, "354" = 0.028307692307692308
, "373" = 0.03327283726557774
, "353" = 0.13589128697042369
)
)
, names = c("logx", "y")
, class = "data.frame"
, row.names = c("141", "125", "140", "124", "139", "123", "122",
"374", "354", "373", "353", "372", "352", "371", "351",
"607", "587", "606", "586", "605",
"585", "604", "584")
)
===================================================================
Vadim Kutsyy, PhD http://www.kutsyy.com
vkutsyy@cytokinetics.com vadim@kutsyy.com
Statistician tel. 650-624-3218
Cytokinetics, Inc fax. 650-624-3010
280 East Grand Avenue
South San Francisco, CA 94080 http://www.cytokinetics.com
===================================================================
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