Performs ratio transformation (normalisation) of RTCA data, as recommended by the producer Roche.

1 | ```
ratioTransform(object, time)
``` |

`object` |
An object of |

`time` |
numeric, the time point used to normalize the whole series of data |

The *xCelligence* software provided by Roche performs ratio
transform implicitly by dividing the time-series impedance measurement
by the value of a selected time point (so-called 'base-time'), for instance 5 hours after
compound transfection, in each cell. The aim of this transformation was to
scale (normalize) the data of different wells, since the normalized
values of all wells are uniformly 1 at the base-time.

However, this method is vulnerable to arbitrary selection of the time point chosen to normalize. It may be helpful to try several base-time values before comparing normalized results.

See `derivativeTransform`

and `rgrTransform`

for other normalization (scaling) possibilities.

An object of `RTCA`

, populated with normalized
value. The normalized values of all wells are uniformly 1 at the base-time.

Jitao David Zhang jitao_david.zhang@roche.com

`smoothTransform`

and `interpolationTransform`

for smoothing and interpolating the RTCA
data. `rgrTransform`

calculates relative growth rate,
`derivativeTransform`

calculates derivatitve. The later two
methods are not sensative to the selection of base-time point.

1 2 3 4 5 6 | ```
require(RTCA)
ofile <- system.file("/extdata/testOutput.csv", package="RTCA")
x <- parseRTCA(ofile)
xNorm <- ratioTransform(x, 35)
``` |

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