Create a new table from a plot constructed from data points

Dear all,

Reading an excel sheet with around 24000 data points, I made a plot. Now I would like to create a new table from this plot with a user-defined interval, let say with only 10 data points. Is it possible to do so in Matlab?

Many thanks in advance.

Bhattarai

Answer 1

[Voss]

% a table with 1000 rows:
t = table((1:1000).',2*(1:1000).'+100,'VariableNames',{'x' 'y'})

t = 1000×2 table
    x      y 
    __    ___

     1    102
     2    104
     3    106
     4    108
     5    110
     6    112
     7    114
     8    116
     9    118
    10    120
    11    122
    12    124
    13    126
    14    128
    15    130
    16    132

% user-defined interval over x:
x_limits = [200 209];

% logical index saying whether each x in the table is within the interval:
idx = t.x >= x_limits(1) & t.x <= x_limits(2);

% new table with x and y but only where x is within the interval:
new_t = table(t.x(idx),t.y(idx),'VariableNames',{'x' 'y'})

new_t = 10×2 table
     x      y 
    ___    ___

    200    500
    201    502
    202    504
    203    506
    204    508
    205    510
    206    512
    207    514
    208    516
    209    518

[aroj bhattarai]

Thank you Benjamin for your interest on my question. But I guess my writing confused you for my objective. Your answer seems to extract specific (X,Y) data points from the given lumpsum data points and to create a new table out of it.

However, my objective is different. As shown in the attached figure A), I have a plot constructed from around 24000 (X,Y) data points where X runs from 1.0 to 1.3987 with data values as:

1.0000, 1.0236, 1.0256, 1.0287, ........, 1.0358, 1.0359, ....., 1.0579, 1.0581, 1.0596, 1.6113, .............., 1.3726, 1.3862, 1.3889, 1.3961, 1.3987.

As shown in figure B), my objective is to assign a user-defined interval/gap/step/space, for example 0.05 in the linear space of X data points in the plot. And from the plot, I would like to extract only 9 (X,Y) data points to be written in a new table, i.e., (1.00, Y1), (1.05, Y2), (1.10, Y3), (1.15, Y4), (1.20, Y5), (1.25, Y6), (1.30, Y7), (1.35, Y8), (1.3987, Y9).

Bhattarai

Answer 2

[aroj bhattarai]

Although non-profesionally coded, sharing the desired answer in case somebody new in MATLAB have similar issue:

Reading the data set from the excel file

[~, ~, raw] = xlsread('C:\Users...\ABC.xlsx','PQR'); % read PQR sheet of ABC excel file

raw(cellfun(@(x) ~isempty(x) && isnumeric(x) && isnan(x),raw)) = {''};

cellVectors = raw(:,[1,11]);

raw = raw(:,[1,2,3,4,5,6,7,8,9,10,11]);

% 8th and 10th column are input X and Y dataset with X = [1.0 1.3987]

Laminp = data(:,8);

Siginp = data(:,10);

Tabulating the dataset

v = table;

llim=1;

ulim=24000;

v.lam = Laminp(1:24000);

v.sig = Siginp(1:24000);

clearvars data raw cellVectors R Laminp Siginp;

lamint(:,1) = v.lam;

Sigint(:,1) = v.sig;

Interpolating the dataset at desired X interval

t = table;

t.lamtab = lamint(:,1); % data acquired from another excel file tabulated in new table t

t.Sigtab = Sigint(:,1);

Lam_coarse = linspace(1, 1.3987, 10); % Coarse X dataset

Sig_coarse = interp1(t.lamtab,t.Sigtab,Lam_course); % Coarse Y dataset

xlswrite('C:\Users...\XYZ.xlsx',Lam_coarse','Data','A1'); % in the 1st column of Data sheet

xlswrite('C:\Users...\XYZ.xlsx',Sig_coarse','Data','B1'); % in the 2nd column of Data sheet

Plotting

figure(1)

plot(lamint(:,1),Sigint(:,1),'o','LineWidth',1.0, 'color','b');

hold on

plot(Lam_coarse,Sig_coarse,'-','LineWidth',1.0, 'color','b');

grid on

hold off