Valuation of CDO with equal amount

library(copula)
#function for CDO spread calculation 
SpreadOfCDO <- function(copula, default.probability, maturity,
  recovery.rate, attachment, detachment, num.path, num.refdebt)
{
  random.copula <- rcopula(copula,num.path)
  num.default <- rowSums(random.copula < default.probability)
  loss.refdebt <- (1-recovery.rate)/num.refdebt*num.default
  loss.tranche <- (pmax(loss.refdebt - attachment,0)-pmax(loss.refdebt - detachment,0))/(detachment-attachment)
  expectation.loss.tranche <- sum(loss.tranche)/num.path
  spread <- -1/maturity*log(1-expectation.loss.tranche)
  return(spread)
}
################  main  ##################
#parameter
NUM.PATH <- 10^3
NUM.REFDEBT <- 100
DEFAULT.PROBABILITY <- 0.05
MATURITY <- 5
RECOVERY.RATE <- 0.4
#copulas which I want to compare.
COPULA <- list(normalCopula(0.15, dim = NUM.REFDEBT),
  tCopula(0.15, dim = NUM.REFDEBT, df = 20),
  tCopula(0.15, dim = NUM.REFDEBT, df = 6),
  tCopula(0.15, dim = NUM.REFDEBT, df = 3),
  claytonCopula(0.21, dim = NUM.REFDEBT)
)
#define for easy programming
SpreadOfCDOWithFixedParameter <- function(copula,attachment, detachment){
  SpreadOfCDO(copula, DEFAULT.PROBABILITY, MATURITY, 
    RECOVERY.RATE, attachment, detachment, NUM.PATH, NUM.REFDEBT)
}
result <- list()
#tranche:equity
result[[1]] <- sapply(COPULA,SpreadOfCDOWithFixedParameter,0.0,0.06)
#tranche:mezzanine
result[[2]] <- sapply(COPULA,SpreadOfCDOWithFixedParameter,0.06,0.18)
#tranche:senior
result[[3]] <- sapply(COPULA,SpreadOfCDOWithFixedParameter,0.18,0.36)
#tranche:super senior
result[[4]] <- sapply(COPULA,SpreadOfCDOWithFixedParameter,0.36,1)
#convert to matrix, and chenge unit to "bp"
result <- 10^4*do.call("cbind", result) 
colnames(result) <- c("equity","mezzanine","senior","super senior")
rownames(result) <- c("normal","t(20)","t(6)","t(3)","clayton")
result