How to quickly find the position of a value in a sorted column data?

I have a list of ascendingly sorted data A = [-80, -79.6, -79.2, -77, 65,... 45]. If there is a value B, how do I quickly find the indices of the two values with one smaller than that and the very next one larger than that? For example, if B=79.8, the two indices will be 1 and 2. If B = 78, the two indices should be 3 and 4.

I know how to write a loop to process this, but my database is huge. As a result, it would take a huge amount of time to process.

Thanks!

Answer 1

[Star Strider]

Try this:

V = linspace(-80, 45, 150);                             % Create Vector
B = -78;
idx = find(V <= B, 1, 'last');
Result = [idx idx+1];

[Leon]

Many thanks!

[Star Strider]

As always, my pleasure!