How to pick the minimum value from column1(flowrate) with respect to each value from column2(head)?

Hi,

I have a data in 2 columns. Column 1 is flowrate and column 2 is head. Head values are like 0,0,0.01,0.01, and up to 0.5 but with respect to head values flow rate values changing even with at the same head

for example:

Head Flowrate

0.5 5.04

0.5 5.15

0.5 5.12

etc etc

I want to plot the graph of head over flowrate by specifying that for each head value plot the minimum flowrate value for example if at 0.5 head flowrate have a range from (5.04-5.12) it will plot 5.04... This way I can ignore the discrepencies and analyse the data.

Below is the code for only plotting the data but not with the minimum flow rate value, I am also attaching the csv file. Your help will be much appreciated.

Code so far:

files = ['F:\19-CFD_Analysis\LES\K-Equation\110_Outlet\Fine_1\S_Curve\S-Curve.csv'];

a = readmatrix(files);

x=a(:,1);

y=a(:,2)*1000;

plot(x,y,'*')

xlim([0 6])

ylim([0 500])

Answer 1

[David Hill]

s=readmatrix('S-Curve.csv');
a=[];
u=unique(s(:,2));
for k=1:length(u)
    m=min(s(s(:,2)==u(k),1));
    a=[a,m(1)];
end
plot(u,a);

[muhammad choudhry]

perfect! Thanks alot. I am trying to understand what the bottom 2 lines doing in the code can you give me a little explanation please,

m=min(s(s(:,2)==u(k),1));

a=[a,m(1)];

Thanks in advance

[David Hill]

This is better.

s=readmatrix('S-Curve.csv');
u=unique(s(:,2));
a=zeros(1,length(u));%preallocate
for k=1:length(u)
    a(k)=min(s(s(:,2)==u(k),1));%s(:,2)==u(k) finds all column 2 values equal to u(k), then min(s(that,1)) finds min of all column 1 rows that correspond
end
plot(u,a);

[muhammad choudhry]

THANKS ALOT FOR THE EXPLANATION