what is meant by censored data why is there censored points in data set are there models to measure censored crime? what is the problem with natural barriers in cities? what is natural barrier? what is natural censored why is natural censoring necessary in data sets what is the natural barrier? what are natural barriers? why does a poisson model fail why is censoring a problem why is there censoring of crime locations what is natural barrier model what makes a city censored what are natural barriers in data what is the problem with natural barriers what model does natural barriers use what is the natural barrier in a crime point model what is the nature of censoring of the data? what is the definition of natural barriers in a population-based model?