add title to xaxis

projects/project-3/frontend/src/app/dashboard/dashboard.component.html

@@ -188,7 +188,7 @@
           <mat-card-title>Rental Time</mat-card-title>
           <mat-card-subtitle>
             This chart shows the workload of the currently selected Station in relation
-            of the time of the day. It is visualized at which time of the day a journey begins or ends.
+            of the time of the day. It is visualized at which time of the day a journey begins or ends (blue).
             In addition, the average rental duration of the trips is displayed at the given time (green).
           </mat-card-subtitle>
         </mat-card-header>

projects/project-3/frontend/src/app/dashboard/dashboard.component.ts

@@ -297,6 +297,9 @@ export class DashboardComponent implements OnInit {
           colors: ['transparent']
         },
         xaxis: {
+          title: {
+            text: 'average rental duration'
+          },
           categories: minutesGroup,
           labels: {
             formatter: value => {
@@ -358,6 +361,9 @@ export class DashboardComponent implements OnInit {
           curve: 'straight'
         },
         xaxis: {
+          title: {
+            text: 'time of the day'
+          },
           categories: timeFrame,
           tickAmount: 24,
           tickPlacement: 'between',
@@ -454,6 +460,9 @@ export class DashboardComponent implements OnInit {
           colors: ['transparent']
         },
         xaxis: {
+          title: {
+            text: 'average rental duration'
+          },
           categories: minutesGroup,
           labels: {
             formatter: value => {
@@ -513,6 +522,9 @@ export class DashboardComponent implements OnInit {
           curve: 'straight'
         },
         xaxis: {
+          title: {
+            text: 'time of the day'
+          },
           categories: timeFrame,
           tickAmount: 24,
           tickPlacement: 'between'