legend color is not match

hi,guys,

my code is to plot 3 sets of data,in blue ,red and green respectively, however, the legend is not match for the third one (it is the same with the 2rd one), can anyone help me?

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clear

filename = '1.log';

set = 768;

fid = fopen(filename,'r');

[num1,num2] = textread(filename,'%d%d');

lines = get_lines(fid);

length = 1:1:lines;

title('haha');

xlabel('hehe');

ylabel('heihei');

plot(length,num1,'-b*',length,set,'-r',length,num2,'-go');

hleg = legalpha('1','2','3');

fclose('all');

the results:

Answer 1

[Michael Haderlein]

Huh, there's a lot to comment.

1. To your question: Let me copy the important lines:

set = 768;
length = 1:1:lines;
plot(length,num1,'-b*',length,set,'-r',length,num2,'-go');

"set" has only one value, length has multiple values. When you do something like

 plot(1:3,1,'-r'), legend show

you'll create 3 plots with equal style. The only thing which puzzles me is that you can see the red line. I expected no red line to be visible as each plot has only one point and there's no line to print.

What you can do is to plot it like this:

 plot([1 lines],[set set],'-r')

Then, please see some additional comments:

2. "length" is a built-in function. Don't use this as variable name as this might cause odd and unexpected behavior of your program.

3. If you create an array with an increment of 1, you don't need to specify this increment. Just myarray=1:lines is fine (I don't want to use "length" as variable name again).

4. I don't know this get_lines function, but as you have already read the content of the file, a simple

lines=length(num1);

will do the same job. As long as you didn't create a variable called length ;-)

5. Close the file soon as possible (here, right after the textread) and just specify the file identifier.

 fclose(fid);

If you work with multiple files, a general fclose('all') might cause errors which are tricky to find.

Some of these remarks might sound pedantic but learning a good programming style from the beginning will help you a lot later.

[Justin]

thanks Michael! I modified my code as:

------------------------------------------------------

clear

filename = '1.log';

set = 768;

fid = fopen(filename,'r');

[num1,num2] = textread(filename,'%d%d');

lines = length(num1);

myarray = 1:lines;

fclose(fid);

title('haha');

xlabel('hehe');

ylabel('heihei');

plot(myarray,num1,'-b*',[1 lines],[set set],'-r',myarray,num2,'-go')

hleg = legalpha('1','2','3');

------------------------------------------------

and it shows!

is this version looks better? lol

and one more question, why the title, xlabel, ylabel are not shown? did I put them in the wrong place?

[Michael Haderlein]

It does :)

Yes, title, xlabel and ylabel are in the wrong place. plot() will delete them. First plot, then title and label the axes. Alternatively, first set "hold all" and then plot. That will also prevent the title and the labels to be deleted.

[Justin]

yes, solved! this is my first time to write matlab script, thank you so much!

Answer 2

[Adam]

length,set,'-r'

in your plot instruction will not give what you want.

you should use

[1 lines], [set set], '-r'

instead because your x and y must have the same number of values to be a single line plot rather than hundreds of individual plots.

Incidentally, don't call a variable 'length'. There is a function called length and even if it doesn't cause you problems here it is sure to in the future if you hide the function name under a variable name.

[Justin]

thank you! you catch the point! but Michael's answer corrects me more, so please forgive me to give the 'accept answer' to him. thanks again!