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aceakash / string-similarity

Finds degree of similarity between two strings, based on Dice's Coefficient, which is mostly better than Levenshtein distance.
MIT License
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compareTwoStrings returning 1 for small and different strings #78

Open Satrofu opened 3 years ago

Satrofu commented 3 years ago

Hello everyone, I hope all is doing good. I found a case in which there is a difference (search for <_15>), the difference is that the first string has <_15>FLL while the second one has <_15>ORD, yet the function is returning 1 as if it were a perfect match. The version used for this comparison was 4.0.1. Below you can see an example ready to be ran in node.js (system version 14.4.0):

const similarity = require("string-similarity");

const body1 = '<REQ><_0>MSG</_0><_1/><_2>55</_2><_3>ORG</_3><_4>F1</_4><_5>MIA</_5><_6>07560685</_6><_7>AC30</_7><_8>HFD</_8><_9>F1</_9><_10>T</_10><_11>US</_11><_12>USD</_12><_13>ZE</_13><_14>ODI</_14><_15>FLL</_15><_16>ORD</_16><_17>UNT</_17><_18>5</_18><_19>1</_19><_20>UNZ</_20><_21>1</_21><_22>000000</_22><_23/></REQ>';

const body2 = '<REQ><_0>MSG</_0><_1/><_2>55</_2><_3>ORG</_3><_4>F1</_4><_5>MIA</_5><_6>07560685</_6><_7>AC30</_7><_8>HFD</_8><_9>F1</_9><_10>T</_10><_11>US</_11><_12>USD</_12><_13>ZE</_13><_14>ODI</_14><_15>ORD</_15><_16>FLL</_16><_17>UNT</_17><_18>5</_18><_19>1</_19><_20>UNZ</_20><_21>1</_21><_22>000000</_22><_23/></REQ>';

console.log(similarity.compareTwoStrings(body1, body2));

Thanks!

dlnnlsn commented 2 years ago

The documentation is misleading when it claims that having a similarity of 1 indicates identical strings. In fact, the Dice coefficient of your two strings is 1 since they contain exactly the same bigrams, just in a different order. An even shorter example is that the Dice coefficient of the strings aba and bab is 1, since in each case the two bigrams in the string are ab and ba.