Update format_p.R to remove leading zeros consistently

[ianhussey]

Previously, leading zeros were only removed when the value was truncated. format_p(.02) would return "p = 0.02" but format_p(.00002) would return "p < .001". APA style suggests always dropping leading zeros from p-values. This commit adds a new argument, leading_zeros, which defaults to FALSE. When FALSE, a gsub() call removes the leading zero before the decimal_seperator.

[gemini-code-assist]

Summary of Changes

Hello @ianhussey, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the format_p function to ensure consistent adherence to APA style guidelines regarding the display of p-values. The primary change involves modifying how leading zeros are handled, making their removal a default behavior rather than being conditional on truncation. This enhancement improves the uniformity and readability of formatted p-values across all cases.

Highlights

• New leading_zero argument: A new boolean argument, leading_zero, has been introduced to the format_p function. By default, this argument is set to FALSE, which enables the new behavior of removing leading zeros.
• Consistent leading zero removal: The format_p function now consistently removes the leading zero before the decimal separator for all p-values when leading_zero is FALSE. Previously, this removal only occurred when the p-value was truncated (e.g., 'p < .001').
• Enhanced APA style compliance: This change ensures that the format_p function adheres more closely to APA style guidelines, which suggest always dropping leading zeros from p-values for improved readability and consistency.

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[gemini-code-assist]

Code Review

This pull request introduces a new leading_zero argument to format_p() to control the display of leading zeros for p-values, aligning with APA style guidelines. The implementation uses a robust regular expression to handle various p-value formats and custom decimal separators.

My review found a critical issue where the new logic will cause a runtime error due to a variable scoping problem. I've also pointed out a minor typo in the documentation. Once the critical issue is addressed, this change will be a valuable improvement.

[strengejacke]

Thanks! A couple of comments. Could you also increase the dev-version number in the DESCRIPTION file? And please add a small test.

[ianhussey]

I’m sorry to plead ignorance but I have no knowledge or experience writing tests. This package and the admin structures around it are clearly a much more professional enterprise than I have experience with..

…

On 25 Aug 2025, at 16:26, Daniel ***@***.***> wrote: strengejacke left a comment (easystats/insight#1123) <#1123 (comment)> Thanks! A couple of comments. Could you also increase the dev-version number in the DESCRIPTION file? And please add a small test. — Reply to this email directly, view it on GitHub <#1123 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABLWCEB5CEAHK64YP6LK4GD3PMMJVAVCNFSM6AAAAACEX6KPDGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTEMRQGUYTSOBWGE>. You are receiving this because you were mentioned.

[strengejacke]

Don't worry, I can add tests. Could you please look at my comments?

[bwiernik]

For consistency, I think we should include a leading zero in the truncated format "p < 0.001" when leading_zero = TRUE

[strengejacke]

Yes, that should already work. In general, this is a breaking change that will affect all outputs and all snapshot tests. @DominiqueMakowski what do you think about this PR?