Mahdi,
The datapoint y-value can only accept numeric values as of now. Passing the y as numerical values should work fine in your case.
If you are still facing any issue, can you kindly create a sample project reproducing the issue you are facing and share it with us over Google-Drive or Onedrive along with sample data so that we can look into your code, run it locally at our end to understand the scenario better and help you out?
—
Adithya Menon
Team CanvasJS