Cap the amount of buckets with the number of values read

src/app.rs

@@ -67,7 +67,7 @@ pub fn get_app() -> App<'static> {
             Arg::new("intervals")
                 .long("intervals")
                 .short('i')
-                .about("Use that many buckets to classify data")
+                .about("Use no more than this amount of buckets to classify data")
                 .default_value("20")
                 .takes_value(true)
         );

src/main.rs

@@ -88,7 +88,8 @@ fn main() {
     let width = sub_matches.value_of_t("width").unwrap();
     match matches.subcommand_name() {
         Some("hist") => {
-            let intervals = sub_matches.value_of_t("intervals").unwrap();
+            let mut intervals: usize = sub_matches.value_of_t("intervals").unwrap();
+            intervals = intervals.min(vec.len());
             let mut histogram = histogram::Histogram::new(
                 intervals,
                 (stats.max - stats.min) / intervals as f64,