Univariate and Multivariable Cox Regression

When to Use

Use this skill when you need to:

• run univariate and multivariable Cox regression on a clinical survival cohort;
• identify prognostic clinical variables associated with time-to-event outcomes;
• export hazard-ratio tables and then render forest plots from those results.

Typical user requests:

• "Run single-factor and multi-factor Cox regression on this survival dataset."
• "Find prognostic variables from my clinical cohort and give me forest plots."
• "Use futime and fustat to do Cox regression for age, stage, and risk."

When Not to Use

Do not use this skill for:

• nomogram construction or calibration analysis;
• time-dependent ROC analysis or external prognostic model validation;
• feature discovery pipelines beyond the built-in univariate screening rule;
• non-survival outcomes such as binary diagnosis or differential expression.

When to Read External Files

Situation	File to Read	Purpose
Need algorithm details	references/algorithm.md	Statistical workflow, assumptions, and feature-selection rule
Need to run analysis	scripts/main.R	Execute Rscript scripts/main.R <command> [options]
Encounter errors	references/troubleshooting.md	Common SKILL_* errors and fixes
Need CLI examples	references/cli-guide.md	Command-specific argument examples
Need test data	tests/data/	Minimal runnable cohort for smoke testing

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Usage

1. Run Cox Analysis

Rscript scripts/main.R analyze \
  --data_file ./clinical_data.csv \
  --features age,gender,stage,risk \
  --time_col futime \
  --event_col fustat \
  --output_dir ./output/ \
  --seed 42

2. Generate Univariate Forest Plot

Rscript scripts/main.R forest-plot \
  --data_file ./output/table/prognosis_uni_cox_results.xlsx \
  --plot_save ./output/plot/uni_forest_plot.pdf

3. Generate Multivariable Forest Plot

Rscript scripts/main.R multi-forest-plot \
  --data_file ./output/table/prognosis_multi_cox_results.xlsx \
  --plot_save ./output/plot/multi_forest_plot.pdf

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Arguments

Analyze Command

Short	Long	Type	Default	Description
-d	--data_file	character	required	Clinical CSV file with sample IDs as row names
-f	--features	character	age,gender,stage,Tstage,Nstage,Mstage,risk	Comma-separated features for Cox analysis
-t	--time_col	character	futime	Survival time column
-e	--event_col	character	fustat	Event column encoded as 1=event, 0=censored
-u	--skip_univariate	character	false	Skip univariate screening and fit multivariable model on all requested features
-o	--output_dir	character	./output/	Output directory
	--overwrite	flag	FALSE	Allow writing into a non-empty output directory
-s	--seed	integer	42	Random seed for reproducibility
-T	--timeout_seconds	integer	0	Elapsed time limit in seconds; 0 disables timeout

Forest Plot Commands

These arguments apply to both forest-plot and multi-forest-plot.

Short	Long	Type	Default	Description
-d	--data_file	character	required	Cox result table in .xlsx, .xls, or .csv format
-p	--plot_save	character	required	Output PDF path
-w	--width	double	8	Plot width in inches
-H	--height	double	6	Plot height in inches
-F	--font_size	double	11	Font size for forest-plot labels
-s	--seed	integer	42	Random seed for reproducibility
-T	--timeout_seconds	integer	0	Elapsed time limit in seconds; 0 disables timeout

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Input Format

Clinical Data (--data_file for analyze)

CSV file with sample IDs as row names and one column per feature/end-point variable.

",age,gender,stage,futime,fustat,risk
SAMPLE_001,65,Male,StageIII,365,1,high
SAMPLE_002,52,Female,StageII,730,0,low
SAMPLE_003,78,Male,StageIV,180,1,high

Requirements

• The file must be CSV.
• Sample IDs must be stored in the first column as row names.
• time_col must contain finite numeric values greater than 0.
• event_col must contain only 0 and 1.
• All requested features, time_col, and event_col must exist.
• At least 10 complete samples and at least 2 events are required after filtering incomplete rows.

Cox Result Table (--data_file for plot commands)

The plotting commands read the output table created by analyze.

Required columns:

• Characteristics
• Total(N)
• HR (95% CI)
• P value

---

Output Files

Analyze Command

File	Description
table/prognosis_uni_cox_results.xlsx	Univariate Cox result table. Present unless --skip_univariate true
table/prognosis_multi_cox_results.xlsx	Multivariable Cox result table
data/analysis_data.rds	Serialized complete-case dataset used for Cox fitting
session_info.txt	Session info and recorded run parameters

Plot Commands

File	Description
plot/uni_forest_plot.pdf	PDF forest plot generated by forest-plot
plot/multi_forest_plot.pdf	PDF forest plot generated by multi-forest-plot
plot/session_info.txt	Session info and plotting parameters written beside the PDF

Result Table Columns

Column	Description
Characteristics	Variable name for continuous terms, or level label for categorical terms
Total(N)	Number of complete-case samples used for modeling
HR (95% CI)	Hazard ratio with 95% confidence interval
P value	Wald-test p-value formatted to three decimals or <0.001
feature	Source feature corresponding to each row

---

Workflow

Step 1: Validate and Prepare Data

• Read the clinical CSV.
• Check required columns and data types.
• Convert character predictors to factors.
• Remove rows with missing values across requested model variables.

Step 2: Run Univariate Cox Models

• Fit one Cox model per feature when --skip_univariate false.
• Export hazard ratios, confidence intervals, and p-values.

Step 3: Run Multivariable Cox Model

• Use all significant univariate features with p < 0.05.
• If fewer than 3 significant features are found, fall back to all requested features.
• Export adjusted hazard ratios, confidence intervals, and p-values.

Step 4: Generate Forest Plots

• Read the result table.
• Parse HR (95% CI) values.
• Render a one-page PDF forest plot.

---

Examples

Basic Analysis

Rscript scripts/main.R analyze \
  -d tests/data/sample_clinical_survival_data.csv \
  -o tests/expected_output/ \
  --overwrite

Analysis With Selected Features and Overwrite

Rscript scripts/main.R analyze \
  -d clinical_data.csv \
  -f age,gender,stage,risk \
  -o ./results/ \
  --overwrite \
  -T 600

Direct Multivariable Fit Without Univariate Screening

Rscript scripts/main.R analyze \
  -d clinical_data.csv \
  -f age,stage,risk \
  -u true \
  -o ./results/

Plot Generation

Rscript scripts/main.R forest-plot \
  -d ./results/table/prognosis_uni_cox_results.xlsx \
  -p ./results/plot/uni_forest_plot.pdf \
  -w 10 -H 7 -F 12

Rscript scripts/main.R multi-forest-plot \
  -d ./results/table/prognosis_multi_cox_results.xlsx \
  -p ./results/plot/multi_forest_plot.pdf \
  -w 10 -H 7 -F 12

---

Error Handling

Error	Cause	Solution
SKILL_INVALID_PARAMETER	Missing required CLI value, invalid extension, unknown command, unreadable CSV input, invalid clinical values, too few complete samples/events, or Cox model fitting failure caused by unsupported input data	Check argument names, file types, clinical value constraints, and model input suitability
SKILL_FILE_NOT_FOUND	Input file path does not exist	Verify the input path
SKILL_MISSING_COLUMNS	Required columns are absent from the clinical file or plot table	Check column names and spelling
SKILL_EMPTY_DATA	Input file or plot table contains no usable rows	Verify file content and export process
SKILL_PACKAGE_NOT_FOUND	Required R package is missing	Install the listed CRAN package(s)

IF error persists, READ: references/troubleshooting.md

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Testing

Smoke Test With Included Data

Rscript scripts/main.R --help

Rscript scripts/main.R analyze \
  -d tests/data/sample_clinical_survival_data.csv \
  -o tests/expected_output/ \
  --overwrite

Rscript scripts/main.R forest-plot \
  -d tests/expected_output/table/prognosis_uni_cox_results.xlsx \
  -p tests/expected_output/plot/uni_forest_plot.pdf

Rscript scripts/main.R multi-forest-plot \
  -d tests/expected_output/table/prognosis_multi_cox_results.xlsx \
  -p tests/expected_output/plot/multi_forest_plot.pdf

Automated Smoke Test Script

Rscript tests/run_smoke_test.R

Optional shell wrapper:

bash tests/run_smoke_test.sh

Expected Outputs

tests/expected_output/
|-- data/analysis_data.rds
|-- plot/multi_forest_plot.pdf
|-- plot/session_info.txt
|-- plot/uni_forest_plot.pdf
|-- session_info.txt
|-- table/prognosis_multi_cox_results.xlsx
`-- table/prognosis_uni_cox_results.xlsx

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References

1. Cox DR (1972). Regression Models and Life-Tables. Journal of the Royal Statistical Society: Series B.
2. Therneau TM, Grambsch PM (2000). Modeling Survival Data: Extending the Cox Model.
3. Harrell FE (2015). Regression Modeling Strategies.

For detailed algorithm, READ: references/algorithm.md

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Implementation Checklist

• CLI parsing with optparse
• set.seed() for reproducibility
• requireNamespace() dependency checks
• Session info recording
• Timeout parameter exposed as CLI option
• File reading instructions in SKILL.md
• Modular script structure in scripts/
• Test data provided in tests/data/
• Error handling with SKILL_* codes
• References documented in references/

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Last updated: 2026-04-16 | Version: 1.1.0