stem

Plot discrete sequence data

Syntax

stem(Y)
stem(X,Y)
stem(...,'fill')
stem(...,LineSpec)
h = stem(...)
Description

Description

A two-dimensional stem plot displays data as lines extending from the x-axis. A circle (the default) or other marker whose y-position represents the data value terminates each stem. stem(Y) plots the data sequence Y as stems that extend from equally spaced and automatically generated values along the x-axis. When Y is a matrix, stem plots all elements in a row against the same x value. stem(X,Y) plots X versus the columns of Y. X and Y are vectors or matrices of the same size. Additionally, X can be a row or a column vector and Y a matrix with length(X) rows. stem(...,'fill') specifies whether to color the circle at the end of the stem.

stem(...,LineSpec) specifies the line style, marker symbol, and color for the stem plot.

h = stem(...) returns handles to line graphics objects

Examples

Create a stem plot of 10 random numbers.

                y = linspace(0,2,10);
stem(exp(-y),'fill','-.')
axis ([0 11 0 1])
                

Matlab Plot - stem

In this example, we study the 'stem' instruction to plot Matlab functions.
It draws vertical lines (with a little circle at the tip) proportional to the value of the function at that particular horizontal value. 'stem' does not join the circles with a line, and it is very helpful to stress the fact that the function is not continuous but discrete.

Let's assume that we want to plot the following elegant exponential and sinusoidal function:

let's draw a simple discrete function

% Avoid superimposed operations and close previous figs.
clc; clear; close all 
% First, we define 51 values of our independent variable
x = 0 : 2*pi/50 : 2*pi; 
% Second, we define the function to graph
y = exp(-x/3) .* sin(x); 
% Third, we use the 'stem' function to plot discrete values
stem(x,y) 
% We can add title and labels (as strings in arguments)
title('Demonstration of the -stem- function')
xlabel('angle x')
ylabel('f(x)')

And we get the following plot:

If we define our independant variable using less points, as in

x = 0 : 2*pi/20 : 2*pi;

we get the following visual change: