Hello. I'm trying to graph a line with an arrow on top with a height equal to the impulse strength.

For reference, this is what kind of graph I'm trying to produce:
Continuous Time Impulse Function

So far, I've simply done this:
*graph impulse response(a continuous time function)*
hold on;
graphH = stem(0, k3, 'k^', 'filled');
hold off;
set(graphH, 'markersize', 2);

where k3 is the strength of the impulse. This is giving me fairly good results except for the center (as opposed to the tip) of the arrow is on the height of the impulse. It was REALLY bad until I lowered the markersize to 2. This is for a project, and I could easily lose points for having an incorrect height on my impulse if it's not exactly correct.

Help!