Salesforce has released a free version of its Analytics Cloud, and you don’t need a Salesforce account. You can use your own data from CSV or Excel files or import data from Google Sheets. The catch is that the free version won’t let you save your data or the interactive visualization, although you can export a static image. (There are also limits of 20M file size and 2,000 rows for a Google spreadsheet).
All data stays on your own computer.