Added retractions per year on the landing page

Author: egonw

scholia/app/templates/retraction-index.html

@@ -5,6 +5,7 @@
 
 {% block in_ready %}
 
+{{ sparql_to_iframe('retractions-per-year') }}
 {{ sparql_to_table('most-cited-retracted-works') }}
 {{ sparql_to_table('authors_with_many_retractions') }}
 {{ sparql_to_table('venues_with_many_retractions') }}
@@ -17,6 +18,12 @@
 
 <h1>Retractions</h1>
 
+<h2 id="retractions-per-year">Retractions per year</h2>
+
+<div class="embed-responsive embed-responsive-16by9">
+    <iframe class="embed-responsive-item" id="retractions-per-year-iframe"></iframe>
+</div>
+
 <h2 id="most-cited-retracted-works">Most cited retracted works</h2>
 
 <table class="table table-hover" id="most-cited-retracted-works-table"></table>

scholia/app/templates/retraction-index_retractions-per-year.sparql

@@ -0,0 +1,24 @@
+#sparql_endpoint = https://query-scholarly.wikidata.org/sparql
+#sparql_endpoint_name= WDQS scholarly
+#sparql_editurl = https://query-scholarly.wikidata.org/#
+#sparql_embedurl = https://query-scholarly.wikidata.org/embed.html#
+#defaultView:BarChart
+SELECT
+  (STR(?year_) AS ?year)
+  (SUM(?count_) AS ?count)
+WHERE {
+  {
+    SELECT
+      ?year_
+      (COUNT(DISTINCT ?retractedArticle) AS ?count_)
+    WHERE {
+      ?retractedArticle p:P31 ?isRetractedPaperStatement .
+      ?isRetractedPaperStatement ps:P31 wd:Q45182324 .
+      ?isRetractedPaperStatement pq:P580 ?date .
+      BIND(YEAR(?date) AS ?year_)
+    }
+    GROUP BY ?year_
+  }
+}
+GROUP BY ?year_
+ORDER BY DESC(?year_)