Evidence-first money workflow · Personal Money
Spending Trend by Category Analyzer
Analyze multi-month category spending, latest changes, three-month averages, refund effects, and unusual movement with transparent evidence rules.
- 1Prepare
- 2Analyze
- 3Review and export
Prepare the evidence
Paste the documented CSV schema or choose a local CSV file. Nothing is sent to Nirmion.
Review the analysis
Summary metrics lead back to the rows that support them.
Method and interpretation
How to use Spending Trend by Category Analyzer
Use this analyzer after categories have been reviewed and you need to see which spending areas changed. It provides a monthly matrix, latest movement, trailing average, and robust unusual-change check so one dramatic percentage does not replace the underlying amounts.
Prepare the input
List ISO date, category, and signed amount for each transaction. Positive values add spending; negative refunds reduce it. Use consistent category labels and one currency. The observed period begins at the earliest imported month and ends at the latest; absent category values inside that range are treated as zero.
Check the worked example
The example supplies four months of groceries and transport plus a grocery refund. Groceries rise sharply in August after the refund is netted, while transport remains close to its recent pattern. The matrix shows the amounts used by the latest-change table.
Read the evidence
Sort attention by absolute latest change, then compare the amount, percent label, three-month average, and unusual check. “New spending” replaces an infinite percentage when the prior month was zero. Fewer than four months receives an evidence warning instead of an anomaly claim.
Calculation method
Transactions are summed by category and calendar month in exact minor units. Latest change = latest month − prior month. The trailing average uses up to three observed months. For four or more months, unusual movement is tested against the median and three median absolute deviations.
Questions this workflow helps answer
Use these questions to confirm that this tool matches the task you need to complete.
- How can I track spending by category across several months?
- Which spending categories changed most from the prior month?
- Is a category movement unusual after refunds, missing months, and recent averages are considered?
Limits and decision boundary
A statistical flag is not a diagnosis. Seasonality, reimbursements, category changes, large one-time purchases, missing rows, and partial current months can create legitimate movement. The tool does not forecast future spending or normalize by household size or inflation.
Common mistake
Do not compare a partial current month with a complete prior month without noting the coverage date. Export complete months or interpret the latest result as month-to-date.
Your pasted values and selected CSV files are processed in this browser tab. This workflow does not connect to a bank, save a budget, or provide financial, tax, legal, or investment advice.
Questions about this workflow
Why is a missing category month zero?
Inside the observed period, no imported activity for that category is represented as zero. This assumption is unsafe when the export itself is incomplete.
How are refunds handled?
Enter them as negative amounts in the original category. They reduce that month’s net category spending.
Why does a category need four months for an unusual flag?
A robust median-based comparison needs enough history to avoid labeling a short sequence as a stable pattern.