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# Example of Plotting Simple 2D Data

Assume you have a numerical model built that has 1 independent variable, and 1 or more dependent variables, for example, a one-dimensional heat transfer problem where T or Q are functions of x. How can you make a simple line plot of the results?

Matlab provides facilities for both reading external data files, and for creating these kinds of plots. Here's a sample data file, simply named 'data':

```  0.00 0.00
0.10 0.01
0.20 0.04
0.30 0.09
0.40 0.16
0.50 0.25
0.60 0.36
0.70 0.49
0.80 0.64
0.90 0.81
1.00 1.00
```

It's an ordered sequence of points, with each row containing an x, y combination. All we want to do here is to turn this data into a simple line graph.

To bring this data file into Matlab, you can use the `load` command:

```  load -ascii data
```

Now we have a 11x2 matrix of numbers in a variable named `data`. We want to strip out each column into a separate variable:

```  x=data(:,1)'; % strip out x axis values
y=data(:,2)'; % strip out y axis values
```

The ' operator is a transpose, and transforms the variable from a column of numbers into a row. It's optional, but I think it's easier to read a row of numbers than a column.

Now we have a consistent set of (x,y) data that's ready to be graphed:

```  plot(x,y)
xlabel('x')
ylabel('y')
zlabel('y = x^2')
title('Simple line plot')
```

The final Matlab program file is shown below:

```  load -ascii data
x=data(:,1)'; % strip out x axis values
y=data(:,2)'; % strip out y axis values
plot(x,y)
xlabel('x')
ylabel('y=x^2')
title('Simple line data plot')
```

The final output is shown below: Filed under: 