reindex the dataframe about data-forge-ts

[ashleydavis]

I'm not sure off the top of my head, I'll have to look up the Pandas reindex function to remember how it works. I'll get back to you in a couple of days.

Maybe you could describe to me the behavior you'd like to see in DataForge?

[erictamhk]

i implement this function by using javascript, i don't know am i do it right, but it work.
i find that the DataFrame.at() is very slow to get a row of data.

`dataForge.DataFrame.prototype.reindex = function(new_index, fill_value = null) {
let newArray = ["tempIndex"].concat(this.getColumnNames());
let pairs = this.toPairs();
let newIndexArray = new_index.toArray();
const dfIndexArray = this.getIndex().toArray();

const filterPairs = pairs.reduce(function(a, e, i) {
if (newIndexArray.indexOf(e[0]) >= 0) {
let obj = e[1];
let idx = e[0];
let newObj = {};
newArray.forEach(val => {
if (val === "tempIndex") {
newObj[val] = idx;
} else {
newObj[val] = obj[val];
}
});
a.push(newObj);
}
return a;
}, []);

const emptyPairs = newIndexArray.reduce(function(a, e, i) {
if (dfIndexArray.indexOf(e) === -1) {
let newObj = {};
newArray.forEach(val => {
if (val === "tempIndex") {
newObj[val] = e;
} else {
newObj[val] = fill_value;
}
});
a.push(newObj);
}
return a;
}, []);`

[ashleydavis]

Reindex won't make at any faster.

Currently at doesn't even use the index. I'll re-write the function at some point so that uses the index.

[shajeeck]

@ashleydavis as you mentioned at doesn't use index, what is the function which uses index to return the row?

[shajeeck]

@ashleydavis Or is it already rewritten as i can see in the docs?
https://github.com/data-forge/data-forge-ts/blob/master/docs/guide.md#getting-a-row-or-value-by-index

[ashleydavis]

The at function takes an index and returns the first value at that index.

The at function is not optimised, so it is quite slow (this can be fixed of course),