daff: data diff
This is a library for comparing tables, producing a summary of their differences, and using such a summary as a patch file. It is optimized for comparing tables that share a common origin, in other words multiple versions of the "same" table.
For a live demo, see:
Install the library for your favorite language:
Other translations are available here:
Or use the library to view csv diffs on github via a chrome extension:
The diff format used by
daff is specified here:
This library is a stripped down version of the coopy toolbox (see http://share.find.coop). To compare tables from different origins, or with automatically generated IDs, or other complications, check out the coopy toolbox.
You can run
daff.rb as a utility program:
$ daff daff can produce and apply tabular diffs. Call as: daff [--color] [--no-color] [--output OUTPUT.csv] a.csv b.csv daff [--output OUTPUT.html] a.csv b.csv daff [--output OUTPUT.csv] parent.csv a.csv b.csv daff [--output OUTPUT.ndjson] a.ndjson b.ndjson daff [--www] a.csv b.csv daff patch [--inplace] [--output OUTPUT.csv] a.csv patch.csv daff merge [--inplace] [--output OUTPUT.csv] parent.csv a.csv b.csv daff trim [--output OUTPUT.csv] source.csv daff render [--output OUTPUT.html] diff.csv daff copy in.csv out.tsv daff in.csv daff git daff version The --inplace option to patch and merge will result in modification of a.csv. If you need more control, here is the full list of flags: daff diff [--output OUTPUT.csv] [--context NUM] [--all] [--act ACT] a.csv b.csv --act ACT: show only a certain kind of change (update, insert, delete) --all: do not prune unchanged rows or columns --all-rows: do not prune unchanged rows --all-columns: do not prune unchanged columns --color: highlight changes with terminal colors (default in terminals) --context NUM: show NUM rows of context --id: specify column to use as primary key (repeat for multi-column key) --ignore: specify column to ignore completely (can repeat) --index: include row/columns numbers from original tables --input-format [csv|tsv|ssv|psv|json]: set format to expect for input --eol [crlf|lf|cr|auto]: separator between rows of csv output. --no-color: make sure terminal colors are not used --ordered: assume row order is meaningful (default for CSV) --output-format [csv|tsv|ssv|psv|json|copy|html]: set format for output --padding [dense|sparse|smart]: set padding method for aligning columns --table NAME: compare the named table, used with SQL sources --unordered: assume row order is meaningless (default for json formats) -w / --ignore-whitespace: ignore changes in leading/trailing whitespace -i / --ignore-case: ignore differences in case daff render [--output OUTPUT.html] [--css CSS.css] [--fragment] [--plain] diff.csv --css CSS.css: generate a suitable css file to go with the html --fragment: generate just a html fragment rather than a page --plain: do not use fancy utf8 characters to make arrows prettier --www: send output to a browser
Formats supported are CSV, TSV, and ndjson.
Using with git
daff git csv to install daff as a diff and merge handler
*.csv files in your repository. Run
daff git for instructions
on doing this manually. Your CSV diffs and merges will get smarter,
since git will suddenly understand about rows and columns, not just lines:
You can use
daff as a library from any supported language. We take
daff on a webpage,
Or if using node outside the browser:
var daff = ;
For concreteness, assume we have two versions of a table,
var data1 ='Country''Capital''Ireland''Dublin''France''Paris''Spain''Barcelona';var data2 ='Country''Code''Capital''Ireland''ie''Dublin''France''fr''Paris''Spain''es''Madrid''Germany''de''Berlin';
To make those tables accessible to the library, we wrap them
var table1 = data1;var table2 = data2;
We can now compute the alignment between the rows and columns in the two tables:
var alignment = daffalign;
To produce a diff from the alignment, we first need a table for the output:
var data_diff = ;var table_diff = data_diff;
Using default options for the diff:
var flags = ;var highlighter = alignmentflags;highlighter;
The diff is now in
data_diff in highlighter format, see
'!' '' '+++' '''@@' 'Country' 'Code' 'Capital''+' 'Ireland' 'ie' 'Dublin''+' 'France' 'fr' 'Paris''->' 'Spain' 'es' 'Barcelona->Madrid''+++' 'Germany' 'de' 'Berlin'
For visualization, you may want to convert this to a HTML table with appropriate classes on cells so you can color-code inserts, deletes, updates, etc. You can do this with:
var diff2html = ;diff2html;var table_diff_html = diff2html;
For 3-way differences (that is, comparing two tables given knowledge
of a common ancestor) use
daff.compareTables3 (give ancestor
table as the first argument).
Here is how to apply that difference as a patch:
var patcher = table1table_diff;patcher;// table1 should now equal table2
For other languages, you should find sample code in the packages on the Releases page.
daff library is written in Haxe, which
can be translated reasonably well into at least the following languages:
- Ruby (using an unofficial haxe target developed for
Some translations are done for you on the
To make another translation, or to compile from source
first follow the Haxe language introduction for the
language you care about. At the time of writing, if you are on OSX, you should
install haxe using
brew install haxe. Then do one of:
make js make php make py make java make cs make cpp
For each language, the
daff library expects to be handed an interface to tables you create, rather than creating them
itself. This is to avoid inefficient copies from one format to another. You'll find a
SimpleTable class you can use if
you find this awkward.
- There's a daff wrapper for R written by Edwin de Jonge, see https://github.com/edwindj/daff and http://cran.r-project.org/web/packages/daff
- There's a hand-written ruby port by James Smith, see https://github.com/theodi/coopy-ruby
- You can browse the
daffclasses at http://paulfitz.github.io/daff-doc/
The SponsorsData Commons Co-op, "perhaps the geekiest of all cooperative organizations on the planet," has given great moral support during the development of `daff`. Donate a multiple of `42.42` in your currency to let them know you care: https://datacommons.coop/donate/.
- http://dataprotocols.org/tabular-diff-format/ : a specification of the diff format we use (appears to have gone away; see https://paulfitz.github.io/daff-doc/spec.html now).
- http://theodi.org/blog/csvhub-github-diffs-for-csv-files : using this library with github.
- https://github.com/ropensci/unconf/issues/19 : a thread about diffing data in which daff shows up in at least four guises (see if you can spot them all).
- http://theodi.org/blog/adapting-git-simple-data : using this library with gitlab.
- http://okfnlabs.org/blog/2013/08/08/diffing-and-patching-data.html : a summary of where the library came from.
- http://blog.okfn.org/2013/07/02/git-and-github-for-data/ : a post about storing small data in git/github.
- http://blog.ouseful.info/2013/08/27/diff-or-chop-github-csv-data-files-and-openrefine/ : counterpoint - a post discussing tracked-changes rather than diffs.
- http://blog.byronjsmith.com/makefile-shortcuts.html : a tutorial on using
makefor data, with daff in the mix. "Since git considers changes on a per-line basis, looking at diffs of comma-delimited and tab-delimited files can get obnoxious. The program daff fixes this problem."
daff is distributed under the MIT License.