Creating A Graph with MATLAB

From time to time situations arise that require the graphing of a solution, with its graphing technology MATLAB provides a convenient and intuitive way of plotting graphs and adding assets to those plots. In this post we will be looking at using MATLAB to create a graph showing the relationship between water temperature and its density.

Table showing the Density of water at various temperatures.

Temp./ oC

Density/ mL

Temp./ oC

Density/ mL

15

0.9991

24

0.973

16

0.9990

25

0.9971

17

0.9988

26

0.9968

18

0.9986

27

0.9965

19

0.9984

28

0.9963

20

0.9982

29

0.9960

21

0.9980

30

0.9957

22

0.9978

31

0.9954

23

0.9976

32

0.9951

Here we go! launch MATLAB.

Enter in the MATLAB command window.

 x = 15:32; 

Enter in the MATLAB command window.

y = [0.9991 0.9990 0.9988 0.9986 0.9984 0.9982 0.9980 0.9978 0.9976 0.973 0.9971 0.9968 0.9965 0.9963 0.9960 0.9957 0.9954 0.9951];

Enter in the MATLAB command window. This will create the initial graph.

plot(x,y, '*-')

Now that we have the initial plot we can move on to adding x and y axis labels and a chart title.

Enter in the MATLAB command window.


ylabel('Density/ mL')

xlabel('Temp./ ºC')

title('Graph showing density of water at various temperatures')


At this point you may be asking yourself, how can this graph help me? well it just so happens that MATLAB has this function called interp1 which allows you to find a y axis value for a given x axis value. We will use this function to find the density of water at any given temperature.

Lets look at the density for water at 26.33 ºC and 27 ºC. In the command window enter.

interp1(x, y,26.33)

The resulting y value = 0.9967

In the command window enter.

interp1(x, y,27)

The resulting y value = 0.9965

Lets graph the solution for x = 26.33 and y = 0.9967

line([26.33 26.33],[0.995 0.9967])

Enter in the MATLAB command window

line([26.33 14],[0.9967 0.9967])

The end :), I hope this helps some chemistry student out there.

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