About Correlation Matrix Online
This tool builds a correlation matrix from a CSV file, an Excel sheet or a pasted table and opens on the Correlation tab, a grid with one row and one column for every numeric column. It is free, needs no sign-up and runs in your browser, so nothing you enter is uploaded.
Each cell shows the Pearson correlation coefficient between two columns, to two decimals, with the diagonal fixed at 1.00. Blue means a positive correlation and red a negative one, and the deeper the colour the stronger it is. Only rows where both values are present are used for each pair, so a column with many gaps is compared on fewer rows than the others.
You need at least two numeric columns. A column counts as numeric when at least 95 percent of its non-missing values are numbers, so text and date columns are left out, and a column with too many words is too. The grid covers the first 30 numeric columns. A dash in a cell means the pair had fewer than two shared rows or one column had no variation. The matrix gives r only: no p-values, no significance stars and no Spearman option. To see two columns as a scatter plot, open the Chart view. Read the matrix as a lead on where to look, not as proof of cause.
How to use Correlation Matrix Online
- Drop a file onto the box, tap it to choose one, or paste a copied file. CSV, TSV, TXT, XLSX and XLS files up to 20 MB are accepted. To paste text instead, use the text box below it.
- For a workbook with several sheets, choose the sheet from the Sheet list that appears.
- Read the Overview: rows, columns, missing values, the delimiter and any columns that held stray values.
- Open Summary for per-column statistics, then Profile for types, percentage missing, distributions and the stray values.
- Open Correlation to see how the numeric columns move together, with blue for positive and red for negative.
- Open Preview to read the rows, 50 per page. Type in the filter box to keep matching rows, and press a column header to sort.
- Open Chart, pick a chart type and a column (two for a scatter plot), or press Open Chart Maker for more chart types.
- Press the download button in Summary to save the column statistics as a CSV file.
Features
- Open .csv, .tsv, .txt, .xlsx and .xls files up to 20 MB, or paste a file or text.
- Parsing runs in a Web Worker for files and pastes, never on every keystroke. The paste box waits half a second after you stop typing.
- Automatic delimiter detection among comma, semicolon, tab and pipe, with quoted fields and a leading byte-order mark handled.
- Excel support through SheetJS, loaded only when a workbook is opened, with a sheet picker.
- Columns are tracked by position, so two columns with the same header stay separate. The second one is shown as "name (2)".
- Majority-type inference: a column is numeric when 95 percent or more of its non-missing values are numbers, and a date column on the same rule. Stray values are listed.
- Missing values recognised as empty cells, NA, N/A, NaN, null, none, nil, a single or double dash and #N/A, in any letter case.
- Per-column count, missing, unique, mean, median, quartiles, minimum, maximum and sample standard deviation.
- Minimum and maximum are found with a loop, so columns of hundreds of thousands of values are safe.
- Pearson correlation matrix of the numeric columns (the first 30 when there are more), using only rows where both values are present.
- Paged preview, 50 rows per page, with a filter and sortable headers, inside a scroll area that works on a phone.
- Chart builder: bar chart of counts, histogram and scatter plot, plus a link to Chart Maker.
- Download of the per-column summary as a CSV file.
Pearson correlation
For each pair of columns A and B, over rows where both have a value:
r = Σ(a − ā)(b − b̄) / √( Σ(a − ā)² × Σ(b − b̄)² )Worked examples
The built-in sample (age and score for five people) gives age and score: r = 0.42. The matrix is 2 by 2 with 1.00 on the diagonal.
Five rows is too few to rely on. A correlation of 0.42 in five people could easily be chance.
x 1, 2, 3, 4, 5; y 2, 4, 6, 8, 11; z 10, 8, 6, NA, 2 gives x and y: 1.00 (0.9959 before rounding). x and z: -1.00. y and z: -1.00 (-0.9981 before rounding).
The NA row is skipped for any pair that includes z, so those pairs use four rows.
Privacy: how it works
- Files are read by your browser and parsed by JavaScript in a worker on this page. The contents are not sent to Ulkaa or to any other server. The Excel reader is part of this site and loads from it, not from a third party, and only when you open a workbook.
- Nothing is stored. Reloading the page clears everything. The summary CSV is created on your device when you press the download button.
Tips
- If a column you expected to be numeric shows as text, open Profile and read its stray values. A currency symbol, a decimal comma or a word is usually the cause.
- Check the missing count before looking at averages. A mean computed from only 60 percent of the rows can mislead.
- A correlation matrix only covers numeric columns. Encode a yes or no column as 1 and 0 first if you want it included.
- Quote any field that contains your delimiter, such as "1,200" in a comma file, so the row keeps its column count.
- For a very large file, open it instead of pasting it. The paste box is meant for small pastes.
- Delimiter detection looks at the first five lines. Make sure they use the same separator as the rest.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial and no credit card. Ulkaa Tool does the work with your own device, so there is no server bill to pass on to you.
Do I need an account?
No. There is no sign-up and no login. Open the page and use it. An Ulkaa account is not needed for anything on this tool.
Does it run in my browser?
Yes. Your data are processed by code running in your browser tab, on your own device.
Is my data uploaded?
No. Your data are never sent to Ulkaa or to anyone else. You can check this yourself by watching the Network tab in your browser developer tools while you use the tool.
What does the colour in the matrix mean?
Blue cells are positive correlations and red cells are negative ones. The stronger the correlation, the deeper the shade. Values near 0 are nearly uncoloured.
Why are some of my columns missing from the matrix?
Only numeric columns are included. A column counts as numeric when at least 95 percent of its non-missing cells are numbers, so a column with many words is left out. The Profile view lists the stray values.
How are missing values treated?
Each pair uses only the rows where both columns have a number. Empty cells, NA, N/A, NaN, null and a few other markers count as missing.
Does a strong correlation mean one thing causes the other?
No. Correlation only measures how closely two columns move together in a straight line. Another factor, or chance, can produce the same pattern.
More CSV, Excel and Data Analyzer pages
- CSV, Excel and Data AnalyzerOpen a CSV, TSV or Excel file, or paste text, and profile every column: types, missing values, statistics, charts and correlations.
- CSV Analyzer OnlinePer-column statistics for a CSV file, in the Summary view.
- CSV Viewer OnlineLook at your CSV as a table, with a filter box and sortable columns.
- Excel Data AnalyzerOpen an Excel workbook, pick a sheet and get column statistics.
- Excel Viewer OnlineOpen an Excel file, choose a sheet and read it as a table.
- Data Profiling Tool OnlineA column-by-column profile of a CSV, an Excel sheet or a pasted table.