vlad (version 0.1.0)

racusum_arloc_sim: Compute Out of Control ARLs of RA-CUSUM control charts using simulation

Description

Compute Out of Control ARLs of RA-CUSUM control charts using simulation.

Usage

racusum_arloc_sim(r, coeff, coeff2, h, df, R0 = 1, RA = 2, RQ = 1)

Arguments

r

Integer vector. Number of runs.

coeff

NumericVector. Estimated coefficients \(\alpha\) and \(\beta\) from the binary logistic regression model.

coeff2

NumericVector. Estimated coefficients \(\alpha\) and \(\beta\) from the binary logistic regression model of a resampled dataset.

h

double. Control Chart limit for detecting deterioration/improvement.

df

DataFrame. First column are Parsonnet Score values within a range of zero to 100 representing the preoperative patient risk. The second column are binary (0/1) outcome values of each operation.

R0

double. Odds ratio of death under the null hypotheses.

RA

double. Odds ratio of death under the alternative hypotheses. Detecting deterioration in performance with increased mortality risk by doubling the odds Ratio RA=2. Detecting improvement in performance with decreased mortality risk by halving the odds ratio of death RA=1/2.

RQ

double. Defines the performance of a surgeon with the odds ratio ratio of death Q.

Value

Returns a single value which is the Run Length.

References

Steiner SH, Cook RJ, Farewell VT and Treasure T (2000). <U+201C>Monitoring surgical performance using risk-adjusted cumulative sum charts.<U+201D> Biostatistics, 1(4), pp. 441-452. doi: 10.1093/biostatistics/1.4.441.

Examples

# NOT RUN {
library("vlad"); library("ggplot2")
## Set seed for reproducibility
RNGkind("L'Ecuyer-CMRG")
## Datasets
data("cardiacsurgery")
s5000 <- dplyr::sample_n(cardiacsurgery, size=5000, replace=TRUE)
df1 <- subset(cardiacsurgery, select=c(Parsonnet, status))
df2 <- subset(s5000, select=c(Parsonnet, status))

## Estimate coefficients from logit model
coeff1 <- round(coef(glm(status~Parsonnet, data=df1, family="binomial")), 3)
coeff2 <- round(coef(glm(status~Parsonnet, data=df2, family="binomial")), 3)

## Number of simulation runs
m <- 10^3

## Deterioration RA=2:
## 1. Determine critical value for given ARL
h0 <- racusum_arloc_h_sim(L0=370, df=df1, coeff=coeff1, coeff2=coeff2, m=m, RA=2, nc=6)
## 2. Compute Out of Control ARL
RQ <- seq(1, 4, 0.1)
rl <- array(NA, dim=c(m, length(RQ)))
RLS <- sapply(RQ, function(i) {
  cat("RQ: ", i, "\n" )
  rl[, i] <- do.call(c, parallel::mclapply(1:m, racusum_arloc_sim, h=h0, df=df1, RA=2, RQ=i,
                                           coeff=coeff1, coeff2=coeff2, mc.cores=6))
})
df3 <- data.frame(cbind(RQ, "ARL"=apply(RLS, 2, mean), "ARLSE"=apply(RLS, 2, mean)/sqrt(m) ))
ggplot(df3, aes(RQ, ARL)) + geom_line() + theme_classic()

## Improvement RA=1/2:
## 1. Determine critical value for given ARL
h0 <- racusum_arloc_h_sim(L0=370, df=df1, coeff=coeff1, coeff2=coeff2, m=m, RA=1/2, nc=6)
## 2. Compute Out of Control ARL
RQ <- seq(1/4, 1, 1/40)
rl <- array(NA, dim=c(m, length(RQ)))
RLS <- sapply(RQ, function(i) {
  cat("RQ: ", i, "\n" )
  rl[, i] <- do.call(c, parallel::mclapply(1:m, racusum_arloc_sim, h=h0, df=df1, RA=1/2, RQ=i,
                                           coeff=coeff1, coeff2=coeff2, mc.cores=6))
})
df4 <- data.frame(cbind(RQ, "ARL"=apply(RLS, 2, mean), "ARLSE"=apply(RLS, 2, mean)/sqrt(m) ))
ggplot(df4, aes(RQ, ARL)) + geom_line() + theme_classic()
# }