How to create bins that are then used to create surf function

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jgillis16 2015-6-22

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https://ww2.mathworks.cn/matlabcentral/answers/224847-how-to-create-bins-that-are-then-used-to-create-surf-function

评论： Star Strider 2015-6-23

I am trying to create a scatter plot that plots the right ascension against the declination and puts them into 1 degree bins. I have a file and code already that breaks down and takes the right ascension and declination into respective degree variables.

Below is the code:

load GWGCCatalogrm.txt %loads text into workspace
readCatalog( GWGCCatalogrm )
fid = fopen( 'GWGCCatalogrm.txt');
trashLine = fgets(fid); %Skips the first line
data = textscan(fid, '%f%s%f%f%s%f%f%f%f%f%f%f%f%f%f%f%f%f', 'Delimiter', '|', 'TreatAsEmpty','~');
fclose(fid);
GalList.pgc = data{1};
GalList.name = data{2};
GalList.ra = data{3};
GalList.dec = data{4};
GalList.major = data{7};
GalList.abs_mag = data{14};
GalList.dist = data{15};
GalList.ra = GalList.ra.*15;
GalList.dec = GalList.dec ;
GalaxyList = GalList;
C1 = GalList.ra;
S1 = GalList.dec;
c=linspace(-6,10,length(C1));
load NewGalaxy.txt
readCatalog( NewGalaxy )
fid = fopen( 'NewGalaxy.txt');
trashLine = fgets(fid); %Skips the first line
data = textscan(fid, '%f%s%f%f%s%f%f%f%f%f%f%f%f%f%f%f%f%f', 'Delimiter', '|', 'TreatAsEmpty','~');
fclose(fid);
GalList.pgc = data{1};
GalList.name = data{2};
GalList.rad = data{3};
GalList.decd = data{4};
GalList.major = data{7};
GalList.abs_mag = data{14};
GalList.dist = data{15};
GalList.rad = GalList.rad.*15;
GalList.decd = GalList.decd ;
GalaxyList = GalList;
D1 = GalList.rad;
F1 = GalList.decd; 
s=linspace(-6,10,length(D1));
scatter(C1,S1,[],c,'filled')
hold on
scatter(D1,F1)
colorbar
xlim([0 350])
ylim([-90 90])

My files are attached. Thank you!

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Answer 1

Star Strider 2015-6-22

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https://ww2.mathworks.cn/matlabcentral/answers/224847-how-to-create-bins-that-are-then-used-to-create-surf-function#answer_183587

If your data are in fractional degrees, you can use round, fix or their friends to force them into integer degrees.

(I read your earlier post, but couldn’t figure out what you intend by ‘bin’. To me, that infers a histogram, but I then can’t figure out if you want the sum of the numbers of galaxies in a particular interval, and how you want to do that in the context of a 2D scatterplot.)

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Star Strider 2015-6-23

在 MATLAB Online 中打开

The colour definitions are easy. I would use

cm = flipud(colormap(jet(16)));

to define the colours. (You can also use colorbar with your plot.)

Depending on what you want to do, there are a few ways to go with the plot. I would use scatter3, since assigning the colours to the various points is easiest with scatter3. However, each RA-DEC point on the plot would have the same colour for all the galaxies that went into it. (If there is a 1:1 correspondence, that problem disappears.) The scatter3 plot needs vectors, not matrices, but you can do that easily enough by using meshgrid to create the matrices and then creating vectors from them as RA(:), DEC(:) and A(:). They should all match up. You would have a matching vector to define the colours, with one colour for each point, that value going from -6 to +10, but defined as cm(c) where c goes from 1 to 16, with 1 corresponding to -6 and 16 corresponding to 10.

Any element of A that has no galaxies in it (a zero count) would not plot. The best way to do this is:

A(A==0) = NaN;

jgillis16 2015-6-23

在 MATLAB Online 中打开

OK. I keep getting errors so I am just posting what I have so far code wise. Did you manage to produce a plot?

load GWGCCatalog.txt %loads text into workspace
fid = fopen( 'GWGCCatalog.txt');
trashLine = fgets(fid); %Skips the first line
data = textscan(fid, '%f%s%f%f%s%f%f%f%f%f%f%f%f%f%f%f%f%f', 'Delimiter', '|', 'TreatAsEmpty','~');
fclose(fid);
M1=data;
GalList.pgc = data{1};
GalList.name = data{2};
GalList.ra = data{3};
GalList.dec = data{4};
GalList.major = data{7};
GalList.abs_mag = data{14};
GalList.dist = data{15};
GalList.mass =(10.^( (-20.8 - GalList.abs_mag)./ 2.5 )) ; % Converts Absolute Magnitude into (blue luminosity) mass in units of Milky Way (luminosity) mass (how many potential forming stars in region using the blue luminosity which is rough estimate of mass).
GalList.ra = GalList.ra.*15;
GalList.dec = GalList.dec ;
GalaxyList = GalList;
C1 = GalList.ra;
S1 = GalList.dec;
C12 = round(C1);
S12 = round(S1);
A = accumarray([C12+1, S12+90], 1); 
A(A==0)=NaN;
cm = flipud(colormap(jet(17)));
mesh(A)   
[S12,C12] = meshgrid([-89:89], [-0:359]);
scatter3(C12(:), S12(:), A(:), cm(c))

jgillis16 2015-6-23

在 MATLAB Online 中打开

Sorry. It will be column 5 of NewGalaxy.txt, so W1.

code:

load GWGCCatalog.txt %loads text into workspace
fid = fopen( 'GWGCCatalog.txt');
trashLine = fgets(fid); %Skips the first line
data = textscan(fid, '%f%s%f%f%s%f%f%f%f%f%f%f%f%f%f%f%f%f', 'Delimiter', '|', 'TreatAsEmpty','~');
fclose(fid);
M1=data;
GalList.pgc = data{1};
GalList.name = data{2};
GalList.ra = data{3};
GalList.dec = data{4};
GalList.morph = data{5};
GalList.major = data{7};
GalList.abs_mag = data{14};
GalList.dist = data{15};
GalList.mass =(10.^( (-20.8 - GalList.abs_mag)./ 2.5 )) ; % Converts Absolute Magnitude into (blue luminosity) mass in units of Milky Way (luminosity) mass (how many potential forming stars in region using the blue luminosity which is rough estimate of mass).
GalList.ra = GalList.ra.*15;
GalList.dec = GalList.dec ;
GalaxyList = GalList;
C1 = GalList.ra;
S1 = GalList.dec;
load NewGalaxy.txt %loads text into workspace
fid = fopen( 'NewGalaxy.txt');
trashLine = fgets(fid); %Skips the first line
data = textscan(fid, '%f%s%f%f%s%f%f%f%f%f%f%f%f%f%f%f%f%f', 'Delimiter', '|', 'TreatAsEmpty','~');
fclose(fid);
M2=data;
GalList.pgc = data{1};
GalList.name = data{2};
GalList.ra = data{3};
GalList.dec = data{4};
GalList.morph = data{5};
GalList.major = data{7};
GalList.abs_mag = data{14};
GalList.dist = data{15};
GalList.mass =(10.^( (-20.8 - GalList.abs_mag)./ 2.5 )) ; % Converts Absolute Magnitude into (blue luminosity) mass in units of Milky Way (luminosity) mass (how many potential forming stars in region using the blue luminosity which is rough estimate of mass).
GalList.ra = GalList.ra.*15;
GalList.dec = GalList.dec ;
GalaxyList = GalList;
D1 = GalList.ra;
F1 = GalList.dec;
W1 = GalList.morph;

jgillis16 2015-6-23

在 MATLAB Online 中打开

GWGCCatalogrm.txt

Ah, sorry! I am losing my mind (3 hours of sleep is not good!). We can simplify everything by keeping it simple and just concentrating on the file where we removed all the '~' column 5 galaxies --> GWGCCatalogrm.txt (I have attached). Below is the code:

load GWGCCatalogrm.txt %loads text into workspace
fid = fopen( 'GWGCCatalog.txt');
trashLine = fgets(fid); %Skips the first line
data = textscan(fid, '%f%s%f%f%s%f%f%f%f%f%f%f%f%f%f%f%f%f', 'Delimiter', '|', 'TreatAsEmpty','~');
fclose(fid);
M1=data;
GalList.pgc = data{1};
GalList.name = data{2};
GalList.ra = data{3};
GalList.dec = data{4};
GalList.morph = data{5};
GalList.major = data{7};
GalList.abs_mag = data{14};
GalList.dist = data{15};
GalList.mass =(10.^( (-20.8 - GalList.abs_mag)./ 2.5 )) ; % Converts Absolute Magnitude into (blue luminosity) mass in units of Milky Way (luminosity) mass (how many potential forming stars in region using the blue luminosity which is rough estimate of mass).
GalList.ra = GalList.ra.*15;
GalList.dec = GalList.dec ;
GalaxyList = GalList;
C1 = GalList.ra;
S1 = GalList.dec;
W1 = GalList.morph;

Star Strider 2015-6-23

在 MATLAB Online 中打开

I discovered that with some experimenting.

The problem now is that the colour vector ‘c’ is not the same size as the others in the scatter3 argument. I’m not certain how to resolve that, since there are 14435 elements of A(:) that are not NaN, and c has 25673 elements. I’m not certain the mapping would work anyway, because different values of data{5} would likely map to the same value of A. You may have to go without the colours if you want to use the histogram provided by accumarray.

My revised code is:

fid = fopen( 'jgillis16 GWGCCatalogrm.txt');
trashLine = fgets(fid); %Skips the first line
data = textscan(fid, '%f%s%f%f%s%f%f%f%f%f%f%f%f%f%f%f%f%f', 'Delimiter', '|', 'TreatAsEmpty','~');
fclose(fid);
M1=data;
GalList.pgc = data{1};
GalList.name = data{2};
GalList.ra = data{3};
GalList.dec = data{4};
GalList.major = data{7};
GalList.abs_mag = data{14};
GalList.dist = data{15};
GalList.mass =(10.^( (-20.8 - GalList.abs_mag)./ 2.5 )) ; % Converts Absolute Magnitude into (blue luminosity) mass in units of Milky Way (luminosity) mass (how many potential forming stars in region using the blue luminosity which is rough estimate of mass).
GalList.ra = GalList.ra.*15;
GalList.dec = GalList.dec ;
GalaxyList = GalList;
C1 = GalList.ra;
S1 = GalList.dec;
C12 = round(C1);
S12 = round(S1);
A = accumarray([C12+1, S12+90], 1);
A = A(1:360, :);
A(A==0)=NaN;
cm = flipud(colormap(jet(17)));
c = cell2mat(cellfun(@str2num, data{5}, 'Uni',0))+7;    % Define Colour References
[S12M,C12M] = meshgrid([-89:89], [-0:359]);
figure(1)
mesh(S12M, C12M, A)
axis tight
veclens = [size(C12M(:)); size(S12M(:)); size(A(:))];   % Check Vector Lengths
figure(2)
scatter3(C12M(:), S12M(:), A(:), '.')
axis tight

Everything after the cm assignment is new or significantly revised.

jgillis16 2015-6-23

It looks like the 2D plot I produced before attempting this in 3D. This is what I was looking for in terms of binning (the colors are something I have to revise from my side by extracting the color completeness from a few catalogs. It was a nice attempt and I will look further into it.)

Again, thank you so much Star! My questions are done (for now :) ).

Star Strider 2015-6-23

My pleasure!

I searched through the documentation for accumarray and also hist3. Neither provides an index map from the original data to the histogram information. The nested loops would likely work if you have something else you need to do while they’re running, but that also requires that you first decide on how to handle different values of data{5} (e.g. mean, median, sum, product, something else, or simply accumulating them as part of a cell array) for each bin. I have no idea how the galaxies’ sky positions relate to data{5}. If they’re closely correlated, that might not be a problem. It’s something to think about in the interim.

I’ve reserved a specific section of my archive file for your galaxy work, with their URLs, so they all have a context!

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How to create bins that are then used to create surf function

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