Plotting in Excel
For a few series and a modest number of rows, Excel works. Select the time column and the data columns, then insert a scatter chart with straight lines. A line chart places X values as evenly spaced categories, so data recorded at uneven intervals ends up on a distorted time axis.
Excel gets laborious when:
- the file exceeds the worksheet limit of 1,048,576 rows (see how to open CSV files too large for Excel)
- there are many series (a chart holds at most 255), or you want separate axes for different units
- new files in the same format arrive every day and you rebuild the chart each time
Other tools
- Python (matplotlib, etc.): fully flexible and scriptable; requires a Python environment and code.
- gnuplot: free command-driven plotting; you need to learn its syntax.
- Kst: free software for plotting large time-series data; requires installation.
- LOGADEC: time-series viewing and analysis software that runs in your browser. No installation, and the free version includes every viewing and analysis feature.
Plotting a CSV file in LOGADEC
- Start it from Try it in your browser, or download the free version and open the extracted HTML file in Google Chrome or Microsoft Edge.
- Click CSV/Excel and choose your file. The header row, unit row, first data row and X column are detected and highlighted in the preview.
- Select the columns you want and click [Import].
- In the [Series] tab, click [Select all] to show the data.
- Choose a layout: overlay (series on top of each other), stacked (one above another) or two panes side by side for comparison.
- For reports, export the chart as PNG, JPEG, WebP or SVG with [Export image].
Chart operations are covered in the user manual: Working with Graphs.
Common CSV pitfalls and how LOGADEC handles them
| Symptom | Cause | In LOGADEC |
|---|---|---|
| Column names are garbled | Text encoding (Shift_JIS vs UTF-8) | Detected automatically; switch it under [Advanced] if needed |
| Instrument or date lines above the header | Description rows before the header | The header row and first data row are detected and highlighted in the preview |
| A unit row under the column names | Unit row | Read as units and appended to series names, like [rpm] |
| Time column like "2026-10-01 08:00:00" | Date-time text | Recognized as date-time and used as the X axis |
| Semicolon delimiters and decimal commas | European formatting | Files such as "1,50;20,25" are read as is |