ffill

Syntax

ffill(obj, [limit])

Arguments

obj is a vector/matrix/table.

limit is a positive integer.

Details

If obj is a vector: forward fill the NULL values in obj with the previous non-NULL value.

If obj is a matrix or a table: forward fill the NULL values in each column of obj with the previous non-NULL value.

Use the optional parameter limit to limit the number of NULL values to forward fill for each block of NULL values.

This operation creates a new vector and does not change the input vector. Function ffill! changes the input vector.

Examples

$ x=1 2 3 NULL NULL NULL 4 5 6
$ x.ffill();
[1,2,3,3,3,3,4,5,6]

$ x.ffill(1);
[1,2,3,3,,,4,5,6]

$ x.ffill!(2);
$ x;
[1,2,3,3,3,,4,5,6]

$ date=[2012.06.12,2012.06.12,2012.06.13,2012.06.14,2012.06.15]
$ sym=["IBM","MSFT","IBM","MSFT","MSFT"]
$ price=[40.56,26.56,,,50.76]
$ qty=[2200,4500,,5600,]
$ timestamp=[09:34:07,09:35:26,09:36:42,09:36:51,09:36:59]
$ t=table(date,timestamp,sym,price,qty);
$ t;

date	timestamp	sym	price	qty
2012.06.12	09:34:07	IBM	40.56	2200
2012.06.12	09:35:26	MSFT	26.56	4500
2012.06.13	09:36:42	IBM
2012.06.14	09:36:51	MSFT		5600
2012.06.15	09:36:59	MSFT	50.76

$ t.ffill();

date	timestamp	sym	price	qty
2012.06.12	09:34:07	IBM	40.56	2200
2012.06.12	09:35:26	MSFT	26.56	4500
2012.06.13	09:36:42	IBM	26.56	4500
2012.06.14	09:36:51	MSFT	26.56	5600
2012.06.15	09:36:59	MSFT	50.76	5600

select date, timestamp, sym, price.ffill() as price, qty.ffill() as qty from t context by sym;

date	timestamp	sym	price	qty
2012.06.12	09:34:07	IBM	40.56	2200
2012.06.13	09:36:42	IBM	40.56	2200
2012.06.12	09:35:26	MSFT	26.56	4500
2012.06.14	09:36:51	MSFT	26.56	5600
2012.06.15	09:36:59	MSFT	50.76	5600