Matlab - checks on imported data

A bit of background~
I'm using a wii mote to collect accelerometer data, and have the data exported to an excel document.

This data is then imported into matlab using :
a = xlsread(fileName); %reads in file name
x = a(:, xColNum); %time
y1 = a(:, y1ColNum); %accel value x
y2 = a(:, y2ColNum); %accel value y
y3 = a(:, y3ColNum); %accel value z

what i'd like to do next is then set a threshold check so that if any of the values within each of the sets is greater than a decided value a trigger can be set.

I'm not sure how to run the initial check on the y1, y2 ,y3 values. My first thoughts are to run a for loop on the sets and then have if statements that execute when the given values are reached. My only problem is i'm not quite sure how to code this within the m file. Also should it be part of a seperate function of just below the above code.
You could have three flag variables, one for each column, that are initialized to 0 and are set if you find a value that is above the threshold in a particular column. If you're interested only if any value in any of the three columns is above the threshold, you can probably get by with just one flag variable.

flag1 = 0
flag2 = 0
flag3 = 0
Threshold = 10000 % or whatever

for i=1:N
  if y1(i) >= Threshold
    flag1 = 1

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