# Coder - interleave staircases¶

Often psychophysicists using staircase procedures want to interleave multiple staircases, either with different start points, or for different conditions.

There is now a class, psychopy.data.MultiStairHandler to allow simple access to interleaved staircases of either basic or QUEST types. That can also be used from the Loops in the Builder. The following method allows the same to be created in your own code, for greater options.

The method works by nesting a pair of loops, one to loop through the number of trials and another to loop across the staircases. The staircases can be shuffled between trials, so that they do not simply alternate.

Note

Note the need to create a copy of the info. If you simply do thisInfo=info then all your staircases will end up pointing to the same object, and when you change the info in the final one, you will be changing it for all.

from __future__ import print_function
from builtins import next
from builtins import range
from psychopy import visual, core, data, event
from numpy.random import shuffle
import copy, time #from the std python libs

#create some info to store with the data
info={}
info['startPoints']=[1.5,3,6]
info['nTrials']=10
info['observer']='jwp'

win=visual.Window([400,400])
#---------------------
#create the stimuli
#---------------------

#create staircases
stairs=[]
for thisStart in info['startPoints']:
#we need a COPY of the info for each staircase
#(or the changes here will be made to all the other staircases)
thisInfo = copy.copy(info)
#now add any specific info for this staircase
thisInfo['thisStart']=thisStart #we might want to keep track of this
thisStair = data.StairHandler(startVal=thisStart,
extraInfo=thisInfo,
nTrials=50, nUp=1, nDown=3,
minVal = 0.5, maxVal=8,
stepSizes=[4,4,2,2,1,1])
stairs.append(thisStair)

for trialN in range(info['nTrials']):
shuffle(stairs) #this shuffles 'in place' (ie stairs itself is changed, nothing returned)
#then loop through our randomised order of staircases for this repeat
for thisStair in stairs:
thisIntensity = next(thisStair)
print('start=%.2f, current=%.4f' %(thisStair.extraInfo['thisStart'], thisIntensity))

#---------------------
#run your trial and get an input
#---------------------
keys = event.waitKeys() #(we can simulate by pushing left for 'correct')
if 'left' in keys: wasCorrect=True
else: wasCorrect = False

#this trial (of all staircases) has finished
#all trials finished

#save data (separate pickle and txt files for each staircase)
dateStr = time.strftime("%b_%d_%H%M", time.localtime())#add the current time
for thisStair in stairs:
#create a filename based on the subject and start value
filename = "%s start%.2f %s" %(thisStair.extraInfo['observer'], thisStair.extraInfo['thisStart'], dateStr)
thisStair.saveAsPickle(filename)
thisStair.saveAsText(filename)