Stimulus parameter list.
List containing stimulus parameters
with an S3 class attribute of
xcoordinate of the center of stimulus in degrees relative to fixation
ycoordinate of the center of stimulus in degrees relative to fixation
imagean image to display in a machine specific format
is.na(image)then this is a lookup table (vector) for stimulus level at each step of rate Hz in cd/m^2. If image is specified, then this is a list of images, in the same format as image, that is stepped through at rate Hz.
sizediameter of target in degrees, or scaling factor for image if specified
colormachine specific stimulus color settings (ignored if
ratefrequency with which lut is processed in Hz
durationtotal length of stimulus flash in milliseconds. There is no guarantee that
duration %% length(lut)/rate == 0. That is, the onus is on the user to ensure the duration is a multiple of the period of the stimuli.
responseWindowmaximum time (>= 0) in milliseconds to wait for a response from the onset of the stimulus presentation
...machine specific parameters
y are in degrees, with precision to one decimal place recognised.
image is not possible on an Octopus 900.
lut is not possible on an Octopus 900. Stimulus is at 0 dB.
rate is in Hz, with precision to one decimal place recognised.
color is ignored. Use
opiSetBackground() to alter stimulus color.
Andrew Turpin <firstname.lastname@example.org>
Please cite: A. Turpin, P.H. Artes and A.M. McKendrick "The Open Perimetry Interface: An enabling tool for clinical visual psychophysics", Journal of Vision 12(11) 2012.
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# A Size III flickering with a 10Hz square wave at # location (7,7) with luminance 10 dB (HFA) stim <- list(x=7, y=7, size=0.43, color="white", rate=20, # one lut step per 50 ms lut=c(0,318), # so one full lut per 100 ms == 10Hz duration=400, # and 4 cycles per stimulus responseWindow=1500) class(stim) <- "opiTemporalStimulus"