[R] Normalized 2-D cross-correlation

Hi all, I need to do (normalized) 2-D cross-correlation in R. There is a convenient function available in Matlab (see: http://www.mathworks.de/de/help/images/ref/normxcorr2.html). Is there anything comparable in R available? Thanks, Felix [[alternative HTML version deleted]] __

[R] Agreement and Consistency of 2D data

Hi, I have two different imaging modalities (for the identification of areas of infarcted myocardium) that I need to compare regarding agreement and consistency. However, I don't think that methods like Cohen's Kappa, PCC, Bland-Altmann or ICC are sufficient here as there is not just a pairwise bu

Re: [R] Non linear Regression: "singular gradient matrix at initial parameter estimates"

7 > > Ciao! >mario > > > On 12-Apr-11 18:01, Felix Nensa wrote: > >> fit = nls(yeps ~ p1 / (1 + exp(p2 - x)) * exp(p4 * x)) >> >> > -- > Ing. Mario Valle > Data Analysis and Visualization Group| > http://www.csc

Re: [R] Non linear Regression: "singular gradient matrix at initial parameter estimates"

Hi Peter, thank you for your reply. Now I see, that P3 is indeed redundand. But with the simplified model... fit = nls(yeps ~ p1 / (1 + exp(p2 - x)) * exp(p4 * x)) ...nls still produces the same error. Any ideas? Felix 2011/4/12 Peter Ehlers > On 2011-04-11 13:29, Felix Nensa wrote: >

[R] Non linear Regression: "singular gradient matrix at initial parameter estimates"

Hi, I am using nls to fit a non linear function to some data but R keeps giving me "singular gradient matrix at initial parameter estimates" errors. For testing purposes I am doing this: ### R code ### x <- 0:140 y <- 200 / (1 + exp(17 - x)/2) * exp(-0.02*x) # creating 'perfect' samples with fit