Given a vector of sizes of retrieved genes, for each size k, select the top k genes with smallest p values and compute the true positive rate from the retrieved genes and the true positive genes.
FindTpr(pvalue, ind,topk)
A vector of p values, one for each gene, with length m
A vector of indices that the corresponding gene are true positive
A vector of integers ranging from 1 to m , length of retrieved gene list
A vector of True positive rates at given sizes of retrieval.