How do I plot data points with x-axis tick labels that are strings?

hello there, i have 15 (x) points named x1 to x15; and corresponding to this i have 15 (y) points named from y1 to y15. how can i plot them ?

[James Tursa]

Don't create variable names like this in the first place. As you can tell, it becomes hard to work with them downstream in your code. Instead, rewrite your code to produce a single variable named x that has all of the 'x' values, and another variable called y for the 'y' values. Then it is simple:

plot(x,y);

[MAHMOUD ALZIOUD]

i did it but it keeps giving this message: Error using plot Invalid first data argument.

the y values i have are numerical, the x values are strings; example: x1= class1, x2=class2 etc.. y1= 0.05, y2=15 etc

[Marylyn Sammut]

how can you do it with plot(data, ‘.’, (signalNoise,signalTime)

[Walter Roberson]

@Marylyn Sammut

I have the suspicion that you might be attempting to plot variables in a table() object. No currently released version of MATLAB supports that directly; you would need to instead

plot(data.signalTime, data.signalNoise, '.')

Answer 1

[Walter Roberson]

The easiest way to specify the tick labels as strings is to use the xticklabels function. For example, plot five points. Change the ticks to only five values by calling the xticks function. Then change the x-axis tick labels to “x1”, “x2”, “x3”, “x4”, and “x5”. 

plot(1:5) 
xticks(1:5) 
xticklabels(["x1", "x2", "x3", "x4", "x5"]) 

Another way to combine a character with a sequence of numbers is to use the xtickformat function. 

plot(1:5) 
xticks(1:5) 
xtickformat("x %g ") 

Alternatively, you can plot categorical values. Specify the second argument when you call the “categorical” function to ensure that the data is in the expected order. 

x = categorical(["Red", "Yellow", "Blue"],["Red", "Yellow", "Blue"]);
plot(x,1:3)

[MAHMOUD ALZIOUD]

i did it but it keeps giving this message: Error using plot Invalid first data argument.

the y values i have are numerical, the x values are strings; example: x1= class1 x2=class2 etc.. y1= 0.05 y2=15 etc

[Walter Roberson]

You cannot use strings as x coordinates in plot(). You can use integers instead and set the axis xtick positions to the integers and set the xticklabels to the strings. You might also be able to plot using a categorical() as the x axis.

[MAHMOUD ALZIOUD]

thank you very much , this answer makes big sense, can you please provide me with the suitable code for this if you please

[Walter Roberson]

x = {x1, x2, x3, x4, x5, x6, x7, x8, x9};
y = [y1, y2, y3, y4, y5, y6, y7, y8, y9];

plot(y);
set(gca, 'XTick', 1:length(y), 'XTickLabel', x)

[MAHMOUD ALZIOUD]

thank you very much Sir

[harsh jivani]

x = (x1 : x15);
y = (y1 ; y15);

plot(x,y)

[Walter Roberson]

No, that will not work. x1:x15 takes the value in x1 and constructs a vector of consecutive numbers until the value of x15. For example if x1 was 2.7 and x15 were 8.3 then x1:x15 would be [2.7, 3.7, 4.7, 5.7, 6.7, 7.7]

[Ravi Vishwakarma]

@Walter Roberson

you need to just change onething in your program

write plot function like this

Z = plot(x,y)
set(Z,'marker','.','markersize',8)

like this you can plot the graph into dots

[Walter Roberson]

plot(x, y, '.', 'markersize', 8)

[AD]

What if we have large number of data points..say 70?

How can I then obtain a plot in matlab?

[Walter Roberson]

@AD

Please read http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval for information about why we strongly recommend against creating variable names dynamically.

Answer 2

[ejjada]

plz anyone answer me

how to read my hole x axis data as x1,x2,x3,x4,...

[Walter Roberson]

Please read http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval for information about why we strongly recommend against creating variable names dynamically.