Undefined unary operator '-' for input arguments of type 'string error

I am going to show x axis in scatter plot by text label like below with positive and negative signs however I get this error

"Undefined unary operator '-' for input arguments of type 'string' "

Can someone please assist in rectifying?

n= ["-240-260";"-220-240";"-200-220";"-180-200";"-160-180";"-140-160";"-120-140";"-100-120";"-80-100";"-60-80";"-40-60";"-20- 40";"0-20";"0+20";"+20+40";"+40+60";"+60+80";"+80+100";"+100+120";"+120+140";"+140+160";"+160+180";"+180+200";"+200+220";"+220+240"];
y1 = [0,0,0,0,0,0,0,0,0,0,0,0.04,0.32,0.56,0.08,0,0,0,0,0,0,0,0,0,0];
y2 = [0,0.05,0.05,0.05,0,0.1,0,0,0.2,0.3,0.1,0.1,0.05,0,0,0,0,0,0,0,0,0,0,0,0];
x=categorical(n);
plot(x,y1,'r--o', x,y2,'k--o');

[Alan Stevens]

n= ["-240-260";-"220-240";"....

Look carefully at the second entry! I think you should have:

n= ["-240-260";"-220-240";"....

[Rik]

@Alan, you should probably move that to the answer section.

[Elnaz P]

Yes you're right, thanks

but there is another problem, I don't see the x axis regularly, from "-260-240" to "+220+240".

[Rik]

You have told Matlab those strings are categories, so Matlab treated them as categories. Do you want to treat them as bins of a histogram instead?

[Elnaz P]

Yes it is histogram. I am going to sort x axis from "-260-240" to "+220+240". I did x=sort (categorical(n)); but doesn't work. Please see attached photo.

Answer 1

[Steven Lord]

When you call categorical with one input, the list of categories in that categorical is the sorted unique values in the input. From the documentation page:

"B = categorical(A) creates a categorical array from the array A. The categories of B are the sorted unique values from A."

Call categorical with two inputs to keep the categories in your desired order.

"B = categorical(A,valueset) creates one category for each value in valueset. The categories of B are in the same order as the values of valueset"

x = categorical(n, n);

plot(x,y1,'r--o', x,y2,'k--o');

[Elnaz P]

it works, thanks a lot

[Elnaz P]

Hi,

Could I ask another question about change origin point of y axis to (0-20)? I gonna shift Y axis to point (0-20) but I don't have any idea.

ax.XAxisLocation = 'origin';

ax.YAxisLocation = 'origin';

origin = (0-20);

Answer 2

[Alan Stevens]

Why not just:

y1 = [0,0,0,0,0,0,0,0,0,0,0,0.04,0.32,0.56,0.08,0,0,0,0,0,0,0,0,0,0];
y2 = [0,0.05,0.05,0.05,0,0.1,0,0,0.2,0.3,0.1,0.1,0.05,0,0,0,0,0,0,0,0,0,0,0,0];
x=-250:20:230;
plot(x,y1,'r--o', x,y2,'k--o');

This plots the "y" points in the middle of your "x" bands.

[Elnaz P]

Thanks for your help,

but please consider I have

x= ["-240-260";"-220-240";"-200-220";"-180-200";"-160-180";"-140-160";"-120-140";"-100-120";"-80-100";"-60-80";"-40-60";"-20- 40";"0-20";"0+20";"+20+40";"+40+60";"+60+80";"+80+100";"+100+120";"+120+140";"+140+160";"+160+180";"+180+200";"+200+220";"+220+240"];

not exactly x=-250:20:230;

[Alan Stevens]

Where does it differ?