diff --git a/src/app/results/var-results.ts b/src/app/results/var-results.ts
index 1807b0f02958163c81dcd39994aeca8597afdca9..4f7fcf28a6a2b266a73797d91c54e4eeed3f16bb 100644
--- a/src/app/results/var-results.ts
+++ b/src/app/results/var-results.ts
@@ -44,6 +44,9 @@ export class VarResults extends CalculatedParamResults implements PlottableData
     /** size of the longest variated parameter */
     public size: number;
 
+    /** index of the longest variated parameter */
+    public longest: number;
+
     /**
      * tableau des ordonnées du graphe des résultats variés
      */
@@ -60,6 +63,7 @@ export class VarResults extends CalculatedParamResults implements PlottableData
         this._extraResultHeaders = [];
         this.extraResultKeys = [];
         this._yValues = [];
+        this.longest = 0;
     }
 
     public get variatedParameters(): NgParameter[] {
@@ -172,11 +176,14 @@ export class VarResults extends CalculatedParamResults implements PlottableData
 
         // liste la plus longue
         this.size = 0;
+        let i = 0;
         for (const v of this._variatedParams) {
             const s = v.valuesIterator.count();
             if (s > this.size) {
                 this.size = s;
+                this.longest = i;
             }
+            i++;
         }
 
         // valeurs du paramètre à calculer
@@ -202,7 +209,7 @@ export class VarResults extends CalculatedParamResults implements PlottableData
         } else if (this.extraResultKeys.length > 0) {
             defaultY = this.extraResultKeys[0];
         }
-        this.chartX = this.chartX || this.variatedParameters[0].symbol;
+        this.chartX = this.chartX || this.variatedParameters[this.longest].symbol;
         this.chartY = defaultY;
 
         // calculator type for translation