nobs.plm | R Documentation |

This function extracts the total number of 'observations' from a fitted panel model.

```
## S3 method for class 'panelmodel'
nobs(object, ...)
## S3 method for class 'pgmm'
nobs(object, ...)
```

`object` |
a |

`...` |
further arguments. |

The number of observations is usually the length of the residuals
vector. Thus, `nobs`

gives the number of observations actually
used by the estimation procedure. It is not necessarily the number
of observations of the model frame (number of rows in the model
frame), because sometimes the model frame is further reduced by the
estimation procedure. This is, e.g., the case for firstâ€“difference
models estimated by `plm(..., model = "fd")`

where the model
frame does not yet contain the differences (see also
**Examples**).

A single number, normally an integer.

`pdim()`

```
# estimate a panelmodel
data("Produc", package = "plm")
z <- plm(log(gsp)~log(pcap)+log(pc)+log(emp)+unemp,data=Produc,
model="random", subset = gsp > 5000)
nobs(z) # total observations used in estimation
pdim(z)$nT$N # same information
pdim(z) # more information about the dimensions (no. of individuals and time periods)
# illustrate difference between nobs and pdim for first-difference model
data("Grunfeld", package = "plm")
fdmod <- plm(inv ~ value + capital, data = Grunfeld, model = "fd")
nobs(fdmod) # 190
pdim(fdmod)$nT$N # 200
```

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