Looking for an efficient way of finding elements in a cell array of character vectors

I have a cell array of character vectors, named "Channels", in which each entry corresponds a particular EEG channel label. I'd like to find indices that correspond to all P channels. For a single channel, P3, I have no problem. For example,

index = find(strcmp(Channels, 'P3'))

returns the correct index.

To find those indices that correspond to all four P labels, P3, P4, P7, P8, I can "glue" things together, such as

index = find(strcmp(Channels, 'P3')|strcmp(Channels,'P4')|strcmp(Channels,'P7')|strcmp(Channels,'P8'))

Of course, there has to be a more efficient way. I can't seem to find the correct manner to combine 'P3', 'P4', 'P7','P8' so so as to do it one step.

Answer 1

[Stephen23]

Use ismember:

ismember(Channels,{'P3','P4','P7','P8'})

Answer 2

[Paul Fishback]

Thanks very much. The ismember will return a logical array. If I tack on the find command, I get the desired indices as well:

find(ismember(Channels,{'P3','P4','P7','P8'}))