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Hi,   I am working in different formula substitutions using R i have applied linear[lm(y~x)], Quadratic[lm(y~x+I(x^2))] and Cubic[lm(y~x+I(x^2)+I(x^3))] How to use/apply One Term Exponential, Two Term Exponential, Three Term Exponential formulas in R Stat. Regards, Guru [[alternative HTML version deleted]]

...risk default data and am referring to "An introduction to Credit Risk Modelling" by Christian Bluhm. The literature affirms that 'the default frequencies grow exponentially with decreasing credit worthiness'.   I have a data of rating wise default frequencies. The idea is to fit exponentail of the type Y = a * exp( b*X ) where Y is (dependent variable) default frequency and X is rating class code. So e.g. suppose I have rating classes AAA, AA, A.... and so on coded as 1, 2, 3  etc. and suppose the observed default frequencies are  say 0.00011, 0.0029, 0.0083 respectively, then my val...