Zero Upcrossings, Period and Wave height

Hello guys,

I'm not very good with matlab and despite understanding what i have to do "on paper" I need help with the code. I have a huge amount of points (x=time and y=position) describing a non regular wave. I have this to get the data from the Txt.

filename = '/Users/helenapereira/Desktop/A1-Wave Data.txt';

delimiter = '\t';

startRow = 3;

formatSpec = '%f%f%[^\n\r]';

fileID = fopen(filename,'r');

dataArray = textscan(fileID, formatSpec, 'Delimiter', delimiter, 'HeaderLines' ,startRow-1, 'ReturnOnError', false);

fclose(fileID);

Time = dataArray{:, 1};

WAVE = dataArray{:, 2};

clearvars filename delimiter startRow formatSpec fileID dataArray ans;

How can I get the zero upcrossings? (where it goes from negative to positive). Also I believe that I have to interpolate between two values to find the exact x value of y=0.

From the zero upcrossings how can I get the Periods? And the wave height for each period?

Thanks for the help :)