checking for possible divide by zero error.

src/main/java/Simulator.java

@@ -13,6 +13,8 @@ import java.time.Duration;
 import java.util.*;
 import java.util.stream.IntStream;
 
+import static java.lang.Float.*;
+
 //NOTE: "sequence" in method and variable names refers to a peptide sequence from a simulated T cell
 public class Simulator {
     private static final int cdr3AlphaIndex = 0;
@@ -246,7 +248,13 @@ public class Simulator {
         BigDecimal attemptRateTrunc = new BigDecimal(attemptRate, mc);
         //rate of pairing error
         double pairingErrorRate = (double) falseCount / (trueCount + falseCount);
-        BigDecimal pairingErrorRateTrunc = new BigDecimal(pairingErrorRate, mc);
+        BigDecimal pairingErrorRateTrunc;
+        if(pairingErrorRate == NaN || pairingErrorRate == POSITIVE_INFINITY || pairingErrorRate == NEGATIVE_INFINITY) {
+            pairingErrorRateTrunc = new BigDecimal(-1, mc);
+        }
+        else{
+            pairingErrorRateTrunc = new BigDecimal(pairingErrorRate, mc);
+        }
         //get list of well populations
         Integer[] wellPopulations = data.getWellPopulations();
         //make string out of populations list