TimeSeries: assume values are all numbers (#18540)

* assume number for TimeSeries types

* use const

packages/grafana-data/src/utils/processDataFrame.test.ts

@@ -29,6 +29,15 @@ describe('toDataFrame', () => {
     expect(series.fields[0].name).toEqual('Value');
   });
 
+  it('assumes TimeSeries values are numbers', () => {
+    const input1 = {
+      target: 'time',
+      datapoints: [[100, 1], [200, 2]],
+    };
+    const data = toDataFrame(input1);
+    expect(data.fields[0].type).toBe(FieldType.number);
+  });
+
   it('keeps dataFrame unchanged', () => {
     const input = {
       fields: [{ text: 'A' }, { text: 'B' }, { text: 'C' }],

packages/grafana-data/src/utils/processDataFrame.ts

@@ -29,6 +29,7 @@ function convertTimeSeriesToDataFrame(timeSeries: TimeSeries): DataFrame {
     fields: [
       {
         name: timeSeries.target || 'Value',
+        type: FieldType.number,
         unit: timeSeries.unit,
       },
       {