How to create color map?

Hello everybody,

I plot a bargraph by using 2x500, and I need to create a colormap. However it is a bit strange colormap so I need code that, for example, all the values between 15-20 will be blue, all the values between 20-25 will be red and so on. I have never worked with bar colormap and especially with this kind of code. If someone can help I would be very glad.

Thanks in advance.

[Adam Danz]

If you have a screenshot, that might fill in some of the missing info.

For example, is 15-20 1 full bar? 20-25 one full bar?

[Image Analyst]

What is a 2x500 bar graph??? To have each bar be a custom color, see attached demo.

[Adam Danz]

Ilkin Abdullayev's answer moved here as a comment.

Hello,

The bar graph which I have is the same as in the picture that I uploaded. 2x500 was wrong actually I wrote like that by a mistake. So what I have now , a data which contain 7 column and 10000 thousand row. My first column which is a distance in m will be my x axis. And for each distance we have 6 different number which ar represtend in the rest 6 column. So when I plot a bar graph each bar will contain 6 different color. So i need a colormap where I need to specify that for example the numbers between 20 and 25 is blue, between 43 and 50 is red and so on. I hope i explanied clearly.

[Adam Danz]

Still not clear. It sounds like you want to plot a stacked bar graph but there are still some leftover questions. The image you shared isn't a bar graph.

I understand that column 1 defines the x values for each bar but does that mean you expected to have 1000 bars?

Or maybe you want 6 bars each with 1000 segments? Or perhaps the 1000 values are broken up into different bar segements but that isn't explained.

See the link I shared above and try to construct your stacked bar plot, if I interpretted your description correctly, and we can help you out when you get stuck.

[Ilkin Abdullayev]

Yes, I will have thousands bar graph even more since 7×10000 is only a little part of my full data. Thank you for the link I will try to get a result otherwise I will let you know.

[Ilkin Abdullayev]

Hello, I tried stacked bar graph and the resul is good. I have uploaded 2 bar but I will have thousand. So what I need now, is to create a new colormap where I need to specify that for example the number between 15-20 is blue. Then when I plot whereever I will have a value between this range it will trun blue. Not one full column. I mean for example in the picture the second part of both bar from top is red. Then if this red section has a value betwen 15-20 the color will be blue. I have very big data that is why I need a colormap that I can use for all. It is not feasible to change the colors one by one.

Hopefully I explained clearly.

Answer 1

[Adam Danz]

Use a stacked bar graph by entering an nxm matrix which will produce n bars each with m segments.

h = bar(rand(20,40), 'stacked');  % 20 bars, 40 segments each

Change the color of bars 15-20 to blue.

set(h(15:20), 'FaceColor', 'b') 

[Ilkin Abdullayev]

Hello, Sorry for late answer. I found some other way with square scatter but also tried this one and it works.

Just to let to know other that How I got my results:

x=data.a;

y=data.b;

c=deneme13280.Load;

colormap(mymap)

scatter(x, y, [70], c, 's','filled')

xlabel('A');

ylabel('B');

And the reasons to use scatter was that, I need all the pieces of one bar must have same size then I used scatter instead of using my main data in x axis I used it as a color identificator which is c here.

[Adam Danz]

And the result is a bar graph?