# How to use "function\_score" mehod to modify the score for a document?
**URL:** https://discuss.elastic.co/t/how-to-use-function-score-mehod-to-modify-the-score-for-a-document/21842
**Category:** Elasticsearch
**Created:** [January 26, 2015, 11:35pm UTC](https://discuss.elastic.co/t/how-to-use-function-score-mehod-to-modify-the-score-for-a-document/21842 "2015-01-26T23:35:25Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Panzer](https://discuss.elastic.co/u/Panzer)
#### Post date: [January 26, 2015, 11:35pm UTC](https://discuss.elastic.co/t/how-to-use-function-score-mehod-to-modify-the-score-for-a-document/21842/1 "2015-01-26T23:35:25Z")
I have this JSON object where I wish to change the scoring function of the
search query:
POST /index/document/\_search
{
"query": {
"function\_score": {
"query": {"match": {"\_all": "fox"}},
"script\_score": {
"script": "\_score"
}
}
}
}
I want to change the score function so that it multiplies the TF and IDF of
the term "fox". I ran a search query with "\_explain" set to true and in the
explanantion part I got this:
"\_explanation": {
"value": 1.110572,
"description": "weight(text:fox in 76) [PerFieldSimilarity], result of:",
"details": [
{
"value": 1.110572,
"description": "fieldWeight in 76, product of:",
"details": [
{
"value": 1,
"description": "tf(freq=1.0), with freq of:",
"details": [
{
"value": 1,
"description": "termFreq=1.0"
}
]
},
{
"value": 4.442288,
"description": "idf(docFreq=123, maxDocs=3453)"
},
{
"value": 0.25,
"description": "fieldNorm(doc=76)"
}
]
}
]
}
How can use the values of IDF and TF to change the actual score of the
document?
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---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 6, 2017, 12:36am UTC](https://discuss.elastic.co/t/how-to-use-function-score-mehod-to-modify-the-score-for-a-document/21842/2 "2017-07-06T00:36:33Z")