Change colors (of groups) in scatter plot

The following matrix contains around 80 rows, representing 2-dimensional points (each row corresponds to a point), and 3 columns, containing each point's x-coordinate, y-coordinate, and an integer number indicating the group to which the point belongs to, i.e. (-1, 1, 2, 3, 4). The latter integer number, i.e. (-1, 1, 2, 3, 4), comes from a clustering algorithm and it is taken by scatter(x,y,sz,c) to color all the points according to the belonging group. Now, how can I change the colors of the groups of points? I do not know what is the reference color set or color map used by scatter(x,y,sz,c), but can I change it, for example to c = turbo, or other color sets?

a = [37     98      1
     35     94      1
     33     97      1
     33     99      1
     31     96      1
     30     97      1
     29    100      1
     30     94      1
     31     90      1
     28     93      1
     21     63      1
     20     61      1
     22     60      1
     24     60      1
     24     64      1
     27     62      1
     28     65      1
     27     59      1
     23     57      1
     26     56      1
     27     57      1
     29     57      1
     31     60      1
     31     61      1
     31     64      1
     32     66      1
     36     60      1
     37     56     -1
     32     56      1
     31     54      1
     27     53      1
     13     43      2
     17     42      2
     17     40      2
     19     37      2
     14     40      2
     13     42      2
     10     41      2
     10     42      2
      9     39      2
      6     40      2
     25     20      3
     24     18      3
     26     18      3
     27     19      3
     27     21      3
     29     21      3
     30     22      3
     30     23      3
     31     26      3
     33     27      3
     35     28      3
     94     11      4
     95     10      4
     97      8      4
     94      8      4
     93      8      4
     99     12      4
     97     12      4
     98     15      4
     95     14      4
     91     15      4
     92     17      4
     91     19      4
     89     19      4
     87     21      4
     89     22      4
     86     23      4
     84     25      4
     81     25      4
     80     26      4
     82     26      4
     79     29      4
     82     29      4
     83     29      4
     86     28      4
     88     25      4
     91     24      4
     93     21      4
     94     22      4
     94     19      4
     95     18      4
     97     20      4];

scatter(a(:,1),a(:,2),[],a(:,3),'filled','s')

Answer 1

[Rik]

As the documentation explains, you can set the colormap:

a = [37     98      1;     35     94      1;     33     97      1;     33     99      1;     31     96      1;     30     97      1;     29    100      1;     30     94      1;     31     90      1;     28     93      1;     21     63      1;     20     61      1;     22     60      1;     24     60      1;     24     64      1;     27     62      1;     28     65      1;     27     59      1;     23     57      1;     26     56      1;     27     57      1;     29     57      1;     31     60      1;     31     61      1;     31     64      1;     32     66      1;     36     60      1;     37     56     -1;     32     56      1;     31     54      1;     27     53      1;     13     43      2;     17     42      2;     17     40      2;     19     37      2;     14     40      2;     13     42      2;     10     41      2;     10     42      2;      9     39      2;      6     40      2;     25     20      3;     24     18      3;     26     18      3;     27     19      3;     27     21      3;     29     21      3;     30     22      3;     30     23      3;     31     26      3;     33     27      3;     35     28      3;     94     11      4;     95     10      4;     97      8      4;     94      8      4;     93      8      4;     99     12      4;     97     12      4;     98     15      4;     95     14      4;     91     15      4;     92     17      4;     91     19      4;     89     19      4;     87     21      4;     89     22      4;     86     23      4;     84     25      4;     81     25      4;     80     26      4;     82     26      4;     79     29      4;     82     29      4;     83     29      4;     86     28      4;     88     25      4;     91     24      4;     93     21      4;     94     22      4;     94     19      4;     95     18      4;     97     20      4];
scatter(a(:,1),a(:,2),[],a(:,3),'filled','s')
colormap('turbo')

[Sim]

Thanks @Rik, I did not pay enough attention :-)

Answer 2

[Image Analyst]

You should not be using scatter. You should be using gscatter (if you have the stats toolbox) which has the capability you are asking for.

[Sim]

Thanks a lot @Image Analyst! Yes, I can use it, many thanks! :-)