How to plot table T such that column R is for X-axis and column I is for Y-axis and column V is the values between them? (I need to change the shape of dots according to V value such that if it is more than 4.5 for example it plots dot else it is *)

      R        I          V   
    _____    ______    _______

     1000    0.0001      4.901
     2000    0.0001      4.802
     3000    0.0001      4.703
     4000    0.0001      4.604
     5000    0.0001      4.505
     6000    0.0001     4.4059
     7000    0.0001     4.3069
     8000    0.0001     4.2079
     9000    0.0001     4.1089
    10000    0.0001     4.0099
    
 the table has 100 points such that I is from 0.0001 to 0.001 with a 0.0001 increment
  and R is as shown from 1k to 10k with 1k increment for each I value

Answer 1

[Benjamin Kraus]

You cannot use two different markers on a single line, so your best bet is two overlapping lines, and you can use MarkerIndices to control which vertices on your line use markers. For example:

R = 1000:1000:10000;
I = 0.0001*ones(size(R));
V =  [4.901, 4.802,  4.703, ...
    4.604, 4.505, 4.4059, ...
    4.3069, 4.2079, 4.1089, 4.0099];
tbl = table(R,I,V);

% Plot the same line twice
p = plot(tbl.R,tbl.I,tbl.R,tbl.I);

% The first line will have a solid line style, dot markers, and use
% MarkerIndices to control which vertices have markers.
p(1).LineStyle = '-';
p(1).Marker = '.';
p(1).MarkerIndices = find(tbl.V>4.5);

% The second line will have no line style, * markers, and use
% MarkerIndices to control which vertices have markers.
p(2).Color = p(1).Color;
p(2).LineStyle = 'none';
p(2).Marker = '*';
p(2).MarkerIndices = find(tbl.V<=4.5);

[Benjamin Kraus]

Note, if you are using the lastest version of MATLAB, I would leverage two more recent features (table support in the plot command, and SeriesIndex) and write this code a little differently:

R = 1000:1000:10000;
I = 0.0001*ones(size(R));
V =  [4.901, 4.802,  4.703, ...
    4.604, 4.505, 4.4059, ...
    4.3069, 4.2079, 4.1089, 4.0099];
tbl = table(R,I,V);

% Plot the same line twice, leveraging table support in the plot command
% added in R2022a.
p = plot(tbl, "R", ["I", "I"]);

% The first line will have a solid line style, dot markers, and use
% MarkerIndices to control which vertices have markers.
p(1).LineStyle = '-';
p(1).Marker = '.';
p(1).MarkerIndices = find(tbl.V>4.5);

% Make sure both lines use the same color by synchronizing their
% SeriesIndex.
p(2).SeriesIndex = p(1).SeriesIndex;

% The second line will have no line style, * markers, and use
% MarkerIndices to control which vertices have markers.
p(2).LineStyle = 'none';
p(2).Marker = '*';
p(2).MarkerIndices = find(tbl.V<=4.5);