Search for an element in an array in reverse order

for i=1:length(X)  
x=find(Matrix(X(i):1,i)<100,1,'first')'; % 
X100(i)=x; 
end
Unable to perform assignment because the left and right sides have a different number of elements.
Error in MatrixRead (line 16)
X100(i)=x;

I need to find the element less than 100 in reverse order.

help fix this error

X is the item number is greater than 120 (practically I need to get the value 21)

Answer 1

[Stephen23]

Use the 'last' option.