Question regarding error occured

X = importdata('owid-covid-data_2020-21.csv');
john_data = X.textdata;
X_s = string(john_data);
data = X.data;

d = X_s(:,4);
A = zeros(4,396);
n=0;

for i = 1:length(X_s)
    for k = 1:length(data)
        for j = 1:length(d)
            if j < 396
                n = n+1;
                C = X_s(k);
                s_d = d(n(1));
                e_d = d(n);
                N_r = sum((e_d:s_d));
                A = [C, s_d,e_date,N_r]';
                fprintf('%12s %13s %13s %13s\n','Country name', 'Record start date','Record end date','Number of records')
                fprintf('%15f %15f %15f %15f\n',A)
            end
        end
    end
end

The question asked us to pick data from the file which is country that has day tracked less than 396 and print to a table contains Country Name, Record start date, Record end date and number of records in the command window, how am I to find those data and print it to the screen? is my loop have any problem and it won't run

[Jan]

You mention, that an error occurs. Please post a copy of the complete message.

n is a scalar. Then:

s_d = d(n(1));
e_d = d(n);

replies the same value. In consequence

N_r = sum((e_d:s_d));

is the same as:

N_r = e_d;   % or s_d