Compute the Germination index according to Melville et al. (1980) and its modification by de Santana and Ranal (2004) (Ranal and de Santana 2006) .

```
GermIndex(
germ.counts,
intervals,
partial = TRUE,
total.seeds,
modification = c("none", "santanaranal")
)
```

- germ.counts
Germination counts at each time interval. Can be partial or cumulative as specified in the argument

`partial`

.- intervals
The time intervals.

- partial
logical. If

`TRUE`

,`germ.counts`

is considered as partial and if`FALSE`

, it is considered as cumulative. Default is`TRUE`

.- total.seeds
Total number of seeds.

- modification
The modification to be applied. Either

`"none"`

or`"santanaranal"`

. Default is`"none"`

(see**Details**).

The value of the Germination index in the same unit of time as
specified in the argument `intervals`

.

Germination index (\(GI\)) is computed as follows (Melville et al. 1980) .

\[GI = \sum_{i=1}^{k}\frac{\left | \left ( T_{k} - T_{i} \right ) N_{i}\right |}{N_{t}}\]

Where, \(T_{i}\) is the time from the start of the experiment to the \(i\)th interval (day for the example), \(N_{i}\) is the number of seeds germinated in the \(i\)th time interval (not the accumulated number, but the number corresponding to the \(i\)th interval), \(N_{t}\) is the total number of seeds used in the test, and \(k\) is the total number of time intervals.

A modified germination index (\(GI_{mod}\)) was proposed by
(de Santana and Ranal 2004)
where total number of
seeds tested (\(N_{t}\)) is replaced by the total number of germinated
seeds (\(N_{g}\)) in the expression of
Melville et al. (1980)
to
remove the effect of sample size
(Ranal and de Santana 2006)
. It is computed as follows
(Specified by the argument `modification = "santanaranal"`

).

\[GI_{mod} = \sum_{i=1}^{k}\frac{\left | \left ( T_{k} - T_{i} \right ) N_{i}\right |}{N_{g}}\]

The term Germination index (\(GI\)) has also been used to describe the
mathematical expression for Speed of germination
(`GermSpeed`

) by
AOSA (1983)
.

AOSA (1983).
*Seed Vigor Testing Handbook*.
Association of Official Seed Analysts, Ithaca, NY, USA.

de Santana DG, Ranal MA (2004).
*Analise Da Germinacao: Um Enfoque Estatistico*.
Universidade de Brasilia, Brasilia.

Melville AH, Galletta GJ, Draper AD, Ng TJ (1980).
“Seed germination and early seedling vigor in progenies of inbred strawberry selections.”
*HortScience*, **15**(6, I), 749--750.

Ranal MA, de Santana DG (2006).
“How and why to measure the germination process?”
*Brazilian Journal of Botany*, **29**(1), 1--11.

```
x <- c(0, 0, 0, 0, 4, 17, 10, 7, 1, 0, 1, 0, 0, 0)
y <- c(0, 0, 0, 0, 4, 21, 31, 38, 39, 39, 40, 40, 40, 40)
int <- 1:length(x)
# From partial germination counts
#----------------------------------------------------------------------------
GermIndex(germ.counts = x, intervals = int, total.seeds = 50)
#> [1] 5.84
GermIndex(germ.counts = x, intervals = int, total.seeds = 50,
modification = "none")
#> [1] 5.84
GermIndex(germ.counts = x, intervals = int, total.seeds = 50,
modification = "santanaranal")
#> [1] 7.3
# From cumulative germination counts
#----------------------------------------------------------------------------
GermIndex(germ.counts = y, intervals = int, partial = FALSE,
total.seeds = 50)
#> [1] 5.84
GermIndex(germ.counts = y, intervals = int, partial = FALSE,
total.seeds = 50,
modification = "none")
#> [1] 5.84
GermIndex(germ.counts = y, intervals = int, partial = FALSE,
total.seeds = 50,
modification = "santanaranal")
#> [1] 7.3
```