From eda564ed59c129c53913757e50c20c54f1d0e075 Mon Sep 17 00:00:00 2001
From: Damien Elmes <gpg@ankiweb.net>
Date: Sun, 29 Oct 2023 07:43:43 +1000
Subject: [PATCH] Fix D/R graphs excluding values of 1.0 Closes #2783

---
 rslib/src/stats/graphs/eases.rs          | 28 +++++++++++++++++++-----
 rslib/src/stats/graphs/retrievability.rs |  4 ++--
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/rslib/src/stats/graphs/eases.rs b/rslib/src/stats/graphs/eases.rs
index 27b59343f..f4a5092f5 100644
--- a/rslib/src/stats/graphs/eases.rs
+++ b/rslib/src/stats/graphs/eases.rs
@@ -15,7 +15,7 @@ impl GraphsContext {
             if let Some(state) = card.memory_state {
                 *difficulty
                     .eases
-                    .entry(round_to_nearest_five(state.difficulty() * 100.0))
+                    .entry(percent_to_bin(state.difficulty() * 100.0))
                     .or_insert_with(Default::default) += 1;
             } else if matches!(card.ctype, CardType::Review | CardType::Relearn) {
                 *eases
@@ -28,8 +28,26 @@ impl GraphsContext {
     }
 }
 
-pub(super) fn round_to_nearest_five(x: f32) -> u32 {
-    let scaled = x * 10.0;
-    let rounded = (scaled / 5.0).round() * 5.0;
-    (rounded / 10.0) as u32
+/// Bins the number into a bin of 0, 5, .. 95
+pub(super) fn percent_to_bin(x: f32) -> u32 {
+    if x == 100.0 {
+        95
+    } else {
+        ((x / 5.0).floor() * 5.0) as u32
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn bins() {
+        assert_eq!(percent_to_bin(0.0), 0);
+        assert_eq!(percent_to_bin(4.9), 0);
+        assert_eq!(percent_to_bin(5.0), 5);
+        assert_eq!(percent_to_bin(9.9), 5);
+        assert_eq!(percent_to_bin(99.9), 95);
+        assert_eq!(percent_to_bin(100.0), 95);
+    }
 }
diff --git a/rslib/src/stats/graphs/retrievability.rs b/rslib/src/stats/graphs/retrievability.rs
index c1ac3febd..7356b95c3 100644
--- a/rslib/src/stats/graphs/retrievability.rs
+++ b/rslib/src/stats/graphs/retrievability.rs
@@ -5,7 +5,7 @@ use anki_proto::stats::graphs_response::Retrievability;
 use fsrs::FSRS;
 
 use crate::scheduler::timing::SchedTimingToday;
-use crate::stats::graphs::eases::round_to_nearest_five;
+use crate::stats::graphs::eases::percent_to_bin;
 use crate::stats::graphs::GraphsContext;
 
 impl GraphsContext {
@@ -26,7 +26,7 @@ impl GraphsContext {
                 );
                 *retrievability
                     .retrievability
-                    .entry(round_to_nearest_five(r * 100.0))
+                    .entry(percent_to_bin(r * 100.0))
                     .or_insert_with(Default::default) += 1;
             }
         }