How to specify that sometimes the program doesn't have to show a letter stimuli?

I have a text component but sometimes I need to show a letter and sometimes I don’t, how can I specify this in the excel file?

Did you try just leaving the cell blank (or variations, like just a space character)?

Thanks Michael! If I let the cell blank it display: text or the previous letter showed. The space character worked perfectly! Now I have the same problem with the position because I can´t let it blank. I get this error:
value = numpy.array(value, float)
ValueError: could not convert string to float

Andrea

But a position can’t be blank in the way that text content can be. All stimuli need to have a position, even if they aren’t being shown. If it is for an invisible stimulus, the actual position value doesn’t matter, so perhaps just put any old values in there.

A more general solution for making stimuli invisible is to control their opacity (i.e. 1 for visible, 0 for invisible). Again, then their position and contents are not important, as they won’t be seen.

Thanks Michael, your information was really helpful,

Andrea