jsmurf {clampSeg}  R Documentation 
Implements the JumpSegmentation by MUltiResolution Filter (JSMURF) (Hotz et al., 2013). This modelfree multiscale idealization approach works well on medium and large temporal scales. If short events (flickering) occurs, jules
or hilde
should be used instead. The original work (Hotz et al., 2013) assumed homogeneous noise, but an extension to heterogeneous noise was provided in (Pein et al., 2020). Please see the argument family
and the examples for how to access the function correctly depending on whether homogeneous noise is assumed or heterogeneous noise is allowed. Further details about how to decide whether the noise is homogeneous or heterogeneous and whether events are short are given in the accompanying vignette.
If q == NULL
a MonteCarlo simulation is required for computing critical values. Since a MonteCarlo simulation lasts potentially much longer (up to several hours or days if the number of observations is in the millions) than the main calculations, the package saves them by default in the workspace and on the file system such that a second call requiring the same MonteCarlo simulation will be much faster. For more details, in particular to which arguments the MonteCarlo simulations are specific, see Section Storing of MonteCarlo simulations below. Progress of a MonteCarlo simulation can be reported by the argument messages
and the saving can be controlled by the argument option
, both can be specified in ...
and are explained in getCritVal
.
jsmurf(data, filter, family = c("jsmurf", "jsmurfPS", "jsmurfLR",
"hjsmurf", "hjsmurfSPS", "hjsmurfLR"),
q = NULL, alpha = 0.05, sd = NULL, startTime = 0,
locationCorrection = c("deconvolution", "constant", "none"),
output = c("onlyIdealization", "eachStep", "everything"), ...)
data 
a numeric vector containing the recorded data points 
filter 
an object of class 
family 
the parametric family for the multiscale test in JSMURF. 
q 
by default chosen automatically by 
alpha 
a probability, i.e. a single numeric between 0 and 1, giving the significance level to compute 
sd 
a single positive numeric giving the standard deviation (noise level) 
startTime 
a single numeric giving the time at which recording (sampling) of 
locationCorrection 
indicating how the locations of conductance changes are corrected for smoothing effects due to lowpass filtering, if 
output 
a string specifying the return type, see Value 
... 
additional parameters to be passed to

The idealisation (estimation, regression) obtained by JSMURF. If output == "onlyIdealization"
an object object of class stepblock
containing the idealisation. If output == "eachStep"
a list
containing the entries idealization
with the idealisation, fit
with the fit before locations of conductance changes were corrected for filtering, q
with the given / computed critical values, filter
with the given filter and for families "jsmurf"
, "jsmurfPS"
and "jsmurfLR"
sd
with the given / estimated standard deviation. If output == "everything"
a list
containing the entries idealization
with a list
containing the idealisation after each refining step in the local deconvolution
, fit
with the fit before locations of conductance changes were corrected for filtering, q
with the given / computed critical values, filter
with the given filter and for families "jsmurf"
, "jsmurfPS"
and "jsmurfLR"
sd
with the given / estimated standard deviation. Additionally, if locationCorrection == "deconvolution"
, the idealisation has an attribute
"noDeconvolution"
, an integer vector, that gives the segments for which no deconvolution could be performed, since two short segments followed each other, see also details in deconvolveLocally
.
If q == NULL
a MonteCarlo simulation is required to compute the critical values. Since a MonteCarlo simulation lasts potentially much longer (up to several hours or days if the number of observations is in the millions) than the main calculations, multiple possibilities for saving and loading the simulations are offered. Progress of a simulation can be reported by the argument messages
which can be specified in ...
and is explained in the documentation of getCritVal
. Each MonteCarlo simulation is specific to parametric family
, the number of observations and the used filter. But note that also MonteCarlo simulations for a (slightly) larger number of observations n_q
, given in the argument nq
in ...
and explained in the documentation of getCritVal
, can be used, which avoids extensive resimulations for only a little bit varying number of observations, but results in a (small) loss of power. However, simulations of type "vectorIncreased"
or "matrixIncreased"
, i.e. objects of classes "MCSimulationMaximum"
and "MCSimulationVector"
with nq
observations, have to be resimulated if as.integer(log2(n1)) != as.integer(log2(n2))
when the saved simulation was computed with n == n1
and the simulation now is required for n == n2
and nq >= n1
and nq >= n2
. Simulations can either be saved in the workspace in the variable critValStepRTab
or persistently on the file system for which the package R.cache
is used. Moreover, storing in and loading from variables and RDS files is supported. The simulation, saving and loading can be controlled by the argument option
which can be specified in ...
and is explained in the documentation of getCritVal
. By default simulations will be saved in the workspace and on the file system. For more details and for how simulation can be removed see Section Simulating, saving and loading of MonteCarlo simulations in getCritVal
.
Hotz, T., Schütte, O., Sieling, H., Polupanow, T., Diederichsen, U., Steinem, C., and Munk, A. (2013) Idealizing ion channel recordings by a jump segmentation multiresolution filter. IEEE Transactions on NanoBioscience 12(4), 376–386.
Pein, F., Bartsch, A., Steinem, C., Munk, A. (2020) Heterogeneous Idealization of Ion Channel Recordings  Open Channel Noise. arXiv:2008.02658.
Pein, F., TecuapetlaGómez, I., Schütte, O., Steinem, C., Munk, A. (2018) Fullyautomatic multiresolution idealization for filtered ion channel recordings: flickering event detection. IEEE Transactions on NanoBioscience 17(3), 300–320.
getCritVal
, lowpassFilter
, deconvolveLocally
, jules
, hilde
## idealisation of the gramicidin A recordings given by gramA with jsmurf
# the used filter
filter < lowpassFilter(type = "bessel", param = list(pole = 4L, cutoff = 1e3 / 1e4),
sr = 1e4)
# idealisation by JSMURF assuming homogeneous noise
# this call requires a MonteCarlo simulation
# and therefore might last a few minutes,
# progress of the MonteCarlo simulation is reported
idealisation < jsmurf(gramA, filter = filter, family = "jsmurfPS",
startTime = 9, messages = 100)
# detects conductance changes, but misses short events (flickering)
# if they are not of interest the above idealisation is suitable
# otherwise JULES should be used instead
# JSMURF allowing heterogeneous noise
# for illustration, but less appropriate for this dataset
jsmurf(gramA, filter = filter, family = "hjsmurf",
startTime = 9, messages = 100)
# any second call should be much faster
# as the previous MonteCarlo simulation will be loaded
jsmurf(gramA, filter = filter, family = "jsmurfPS",
startTime = 9, messages = 100)
# much larger significance level alpha for a larger detection power,
# but also with the risk of detecting additional artefacts
# in this example much more changes are detected,
# most of them are probably artefacts
jsmurf(gramA, filter = filter, family = "jsmurfPS",
alpha = 0.9, startTime = 9)
# getCritVal was called in jsmurf, can be called explicitly
# for instance outside of a for loop to save run time
q < getCritVal(length(gramA), filter = filter, family = "jsmurfPS")
identical(jsmurf(gramA, q = q, filter = filter, family = "jsmurfPS",
startTime = 9), idealisation)
# more detailed output
each < jsmurf(gramA, filter = filter, family = "jsmurfPS",
startTime = 9, output = "each")
every < jsmurf(gramA, filter = filter, family = "jsmurfPS",
startTime = 9, output = "every")
identical(idealisation, each$idealization)
idealisationEvery < every$idealization[[3]]
attr(idealisationEvery, "noDeconvolution") < attr(every$idealization,
"noDeconvolution")
identical(idealisation, idealisationEvery)
## zoom into a single jump
plot(9 + seq(along = gramA) / filter$sr, gramA, pch = 16, col = "grey30",
ylim = c(20, 50), xlim = c(9.6476, 9.6496), ylab = "Conductance in pS",
xlab = "Time in s")
# idealisation
lines(idealisation, col = "red", lwd = 3)
# idealisation convolved with the filter
ind < seq(9.647, 9.65, 1e6)
convolvedSignal < lowpassFilter::getConvolution(ind, idealisation, filter)
lines(ind, convolvedSignal, col = "blue", lwd = 3)
# idealisation with a wrong filter
# does not fit the recorded data points appropriately
wrongFilter < lowpassFilter(type = "bessel",
param = list(pole = 6L, cutoff = 0.2),
sr = 1e4)
# MonteCarlo simulations are specific the number of observations and the filter
# hence a new simulation is required (if called for the first time)
idealisationWrong < jsmurf(gramA, filter = wrongFilter, family = "jsmurfPS",
startTime = 9, messages = 100)
# idealisation
lines(idealisationWrong, col = "orange", lwd = 3)
# idealisation convolved with the filter
ind < seq(9.647, 9.65, 1e6)
convolvedSignal < lowpassFilter::getConvolution(ind, idealisationWrong, filter)
lines(ind, convolvedSignal, col = "darkgreen", lwd = 3)
# location correction by a constant, almost the same as the local deconvolution
idealisationConst < jsmurf(gramA, filter = filter, family = "jsmurfPS",
locationCorrection = "constant", startTime = 9, messages = 100)
# idealisation
lines(idealisationConst, col = "brown", lwd = 3)
# idealisation convolved with the filter
ind < seq(9.647, 9.65, 1e6)
convolvedSignal < lowpassFilter::getConvolution(ind, idealisationConst, filter)
lines(ind, convolvedSignal, col = "purple", lwd = 3)
# no correction of locations for filter effects, jump location is shifted to the left
idealisationNone < jsmurf(gramA, filter = filter, family = "jsmurfPS",
locationCorrection = "none", startTime = 9, messages = 100)
# idealisation
lines(idealisationNone, col = "black", lwd = 3)
# idealisation convolved with the filter
ind < seq(9.647, 9.65, 1e6)
convolvedSignal < lowpassFilter::getConvolution(ind, idealisationNone, filter)
lines(ind, convolvedSignal, col = "green", lwd = 3)
# local deconvolution can be called separately
identical(deconvolveLocally(idealisationNone, data = gramA, filter = filter, startTime = 9),
idealisation)
# simulation for a larger number of observations can be used (nq = 3e4)
# does not require a new simulation as the simulation from above will be used
# (if the previous call was executed first)
jsmurf(gramA[1:2.99e4], filter = filter, family = "jsmurfPS", startTime = 9,
nq = 3e4, r = 1e3, messages = 100)
# simulation of type "vectorIncreased" for n1 observations can only be reused
# for n2 observations if as.integer(log2(n1)) == as.integer(log2(n2))
# no simulation is required, since a simulation of type "matrixIncreased"
# will be loaded from the fileSystem
# this call also saves a simulation of type "vectorIncreased" in the workspace
jsmurf(gramA[1:1e4], filter = filter, family = "jsmurfPS", startTime = 9,
nq = 3e4, messages = 100, r = 1e3)
# here a new simulation is required
# (if no appropriate simulation is saved from a previous call)
jsmurf(gramA[1:1e3], filter = filter, family = "jsmurfPS", startTime = 9,
nq = 3e4, messages = 100, r = 1e3,
options = list(load = list(workspace = c("vector", "vectorIncreased"))))
# the above calls saved and (attempted to) load MonteCarlo simulations
# in the following call the simulations will neither be saved nor loaded
jsmurf(gramA, filter = filter, family = "jsmurfPS", startTime = 9,
messages = 100, r = 1e3, options = list(load = list(), save = list()))
# only simulations of type "vector" and "vectorInceased" will be saved and
# loaded from the workspace, but no simulations of type "matrix" and
# "matrixIncreased" on the file system
jsmurf(gramA[1:1e4], filter = filter, family = "jsmurfPS",
startTime = 9, messages = 100,
options = list(load = list(workspace = c("vector", "vectorIncreased")),
save = list(workspace = c("vector", "vectorIncreased"))))
# explicit MonteCarlo simulations, not recommended
stat < stepR::monteCarloSimulation(n = length(gramA), family = "jsmurfPS",
filter = filter, output = "maximum",
r = 1e3, messages = 100)
jsmurf(gramA, filter = filter, family = "jsmurfPS", startTime = 9, stat = stat)
# with given standard deviation
sd < stepR::sdrobnorm(gramA, lag = filter$len + 1)
identical(jsmurf(gramA, filter = filter, family = "jsmurfPS", startTime = 9,
sd = sd), idealisation)
# with one refinement step less, but with a larger grid
# progress of the deconvolution is reported
# potential warning for no deconvolution is suppressed
jsmurf(gramA, filter = filter, family = "jsmurfPS", startTime = 9,
gridSize = c(1 / filter$sr, 1 / 10 / filter$sr),
windowFactorRefinement = 2, report = TRUE,
suppressWarningNoDeconvolution = TRUE)