Handle string in metrics

[sachinkbansal]

Discussed in #81

^{Originally posted by satkalra1 August 5, 2021}
Hey,
I was trying the cue observe on the test dataset, to understand its working properly but after defining the anomaly, I found this particular error:

{"stackTrace": "Traceback (most recent call last):\n File "pandas/_libs/lib.pyx", line 2062, in pandas._libs.lib.maybe_convert_numeric\nValueError: Unable to parse string "null"\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n File "/code/ops/tasks.py", line 49, in anomalyDetectionJob\n dimValsData = prepareAnomalyDataframes(datasetDf, anomalyDefinition.dataset.timestampColumn, anomalyDefinition.metric, anomalyDefinition.dimension, anomalyDefinition.top)\n File "/code/access/utils.py", line 17, in prepareAnomalyDataframes\n datasetDf[metricCol] = pd.to_numeric(datasetDf[metricCol])\n File "/opt/venv/lib/python3.7/site-packages/pandas/core/tools/numeric.py", line 155, in to_numeric\n values, set(), coerce_numeric=coerce_numeric\n File "pandas/_libs/lib.pyx", line 2099, in pandas._libs.lib.maybe_convert_numeric\nValueError: Unable to parse string "null" at position 1715\n", "message": "Unable to parse string "null" at position 1715"}

Could you please tell me , where the things are going wrong?