[GitHub] [echarts] pissang commented on a change in pull request #16431: fix(line): using sampling with lttb, NaN point should not be filtered.

[GitBox <gi...@apache.org>]

pissang commented on a change in pull request #16431:
URL: https://github.com/apache/echarts/pull/16431#discussion_r803258012



##########
File path: src/data/DataStore.ts
##########
@@ -983,6 +985,10 @@ class DataStore {
                 }
             }
 
+            if (appendNaNList.length && appendNaNList.length !== frameEnd - frameStart) {
+                newIndices[sampledIndex++] = appendNaNList[0]; // append first NaN point in every bucket

Review comment:
       If we only append the first NaN point. We should use a variable instead of an array because array will cost more. For example:
   
   ```ts
   let firstNaNIndex = -1;
   
   if (isNaN(y) && firstNaNIndex < 0) {
     firstNaNIndex = rawIndex.
   )
   ...
   if (firstNaNIndex >= 0) {
     newIndices[sampledIndex++] = firstNaNIndex;
   }
   ```
   
   The performance is one of the most important indicator when implementing the sampling algorithm. We can check if it's degenerated in the `test/sample-compare.html` case




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