Compute Correlation Matrix for NDJSON Files Online
Compute a Pearson correlation matrix for numeric columns in NDJSON files directly in your browser. Instantly spot which variables move together — colour-coded heatmap, no upload required.
How to compute Correlation Matrix for NDJSON files
- Drop your file onto the upload area. Every numeric column is found and selected.
- Click column names to leave out any you do not want, such as ID or ZIP code columns. At least two must stay selected.
- Click Compute Correlations. A colour-coded matrix appears, blue for positive and red for negative, with values to 3 decimals. Hover a cell for 6 decimals.
- Click Export Matrix CSV to download the matrix with values to 4 decimals.
Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.
Worked example
An estate agent has recent house sales and wants to see which property features move with the sale price before building a pricing model.
Input (NDJSON)
{"floor_area_sqft":1450,"bedrooms":3,"age_years":32,"sale_price":612000}
{"floor_area_sqft":2100,"bedrooms":4,"age_years":8,"sale_price":845000}
{"floor_area_sqft":980,"bedrooms":2,"age_years":55,"sale_price":455000}
{"floor_area_sqft":1720,"bedrooms":3,"age_years":20,"sale_price":701000}
{"floor_area_sqft":2600,"bedrooms":5,"age_years":3,"sale_price":990000}
{"floor_area_sqft":1200,"bedrooms":2,"age_years":41,"sale_price":540000}Settings
- Numeric columns: floor_area_sqft, bedrooms, age_years, sale_price (all selected)
- Export: Export Matrix CSV
Result
| floor_area_sqft | bedrooms | age_years | sale_price | |
|---|---|---|---|---|
| floor_area_sqft | 1.0000 | 0.9830 | -0.9669 | 0.9991 |
| bedrooms | 0.9830 | 1.0000 | -0.9306 | 0.9798 |
| age_years | -0.9669 | -0.9306 | 1.0000 | -0.9721 |
| sale_price | 0.9991 | 0.9798 | -0.9721 | 1.0000 |
The output is always a CSV, whatever the input format, with an empty top-left header cell. Floor area tracks price almost perfectly at 0.9991. Age is strongly negative at -0.9721: older homes sold for less. The diagonal is 1 because each column matches itself, and the matrix is symmetric. With only six rows these values are fragile, and one unusual sale could move them a lot.
Frequently Asked Questions
Which correlation method is used?
Pearson correlation, which measures straight-line relationships. A strong curved relationship can still show a value near 0. Spearman and Kendall are not available.
Why does a cell show NaN or a dash?
NaN means one of the two columns has the same value in every row it shares with the other, or only one shared row exists, so there is no variation to correlate. A dash means there were no rows with values in both columns. In the CSV export a dash becomes an empty cell.
Is there a limit on the number of columns?
There is no fixed limit, but the matrix grows with the square of the column count. Deselect IDs and other columns that are not real measures to keep it readable.
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