Code lin 45 strfind not enough imput arguments. I am confused why this is.

close all;
clearvars;
%clc;
filter_list = {'Sc_30um','V_13um','Ru_8.5um'};
%filter_list = {'Be_10um','B_10um','C_5um','Mg_10um','Al_10um','Ti_12um','V_10um'};
%filter_list = {'Ti_12um','V_10um','Cr_3um','Fe_10um','Cu_10um','Zr_25um','Nb_20um'}
%filter_list = {'Zr_25um','Nb_20um','Mo_7um','Ag_5um','Sn_15um','Ta_3um','W_10um'}
%filter_list = {'Si_10um','Si_5um','Cr_3um','Fe_5um'}
mpath = mfilename('fullpath');
[path, sciptname] = fileparts(mpath);
addpath(genpath(path));
workdir = path;
cd (workdir);
filters = struct;
energy = 10:5:10000;
file_found = struct;
for n_f = 1:length(filter_list)
    strpos = strfind(filter_list{n_f},'_');
    mat_look = filter_list{n_f}(1:strpos-1);
    file_found = dir([filter_list{n_f} '.txt']);
    if isempty(file_found)
        mat_found = dir([mat_look '*']);
        n_d = 0;
        if ~isempty(mat_found)
            while n_d < length(mat_found)
                n_d = n_d +1;
                strpos = strfind(mat_found(n_d).name,'_');
                mat_found(n_d).mat = mat_found(n_d).name(1:strpos-1);
                if ~strcmp(mat_found(n_d).mat,mat_look)
                    mat_found(n_d) = [];
                    n_d = n_d -1;
                else
                    file_found = mat_found(n_d);
                end
            end
        end
    end
    %file_found.str = sscanf(file_found.name,'%s_%fum.txt');
    strpos = strfind(file_found.name,'_');
    file_found.thick = str2double(file_found.name(strpos+1:end-6));
    strpos = strfind(filter_list{n_f},'_');
    data = importdata(file_found.name);
    filters(n_f).filter_string = data.textdata{1,1};
    string_values = textscan(filters(n_f).filter_string,' %s Density=%f Thickness=%f microns');
    filters(n_f).material = char(string_values{1});
    filters(n_f).density = string_values{2};
    filters(n_f).thickness = string_values{3};
    filters(n_f).thickness_ask = str2double(filter_list{n_f}(strpos+1:end-2));
    filters(n_f).rescale = filters(n_f).thickness_ask/filters(n_f).thickness;
    filters(n_f).thickness_rescaled = filters(n_f).thickness*filters(n_f).rescale;
    filters(n_f).label = char(strcat(filters(n_f).material,{' '},num2str(filters(n_f).thickness_rescaled),{'um'}));
    filters(n_f).E = data.data(:,1);
    filters(n_f).T = data.data(:,2).^filters(n_f).rescale;
    filters(n_f).Eint = energy;
    filters(n_f).Tint = interp1(filters(n_f).E,filters(n_f).T,filters(n_f).Eint,'pchip');
end

Error using strfind
Not enough input arguments.

lines_col = lines;
%% Figure 1 with filter transmission
%fig1 = figure('Name','Filter Transmission','Position',[50 50 1450 720]);
fig1 = figure('Name','Filter Transmission','Units','normalized','Position',[0.1 0.18 0.85 0.7]);
set(groot,'CurrentFigure',fig1);
set(gca,'FontSize',24);
hold on;
for n_f = 1:length(filter_list)
   p(n_f) = plot(filters(n_f).Eint/1e3,filters(n_f).Tint,'-','LineWidth',2,'DisplayName',filters(n_f).label); %#ok<SAGROW>
end
q(1) = patch([4100 4900 4900 4100]/1e3,[1e-6 1e-6 1 1],'b','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Xe L-shell');
%q(2) = patch([3000 3200 3200 3000]/1e3,[1e-6 1e-6 1 1],'r','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Ar K-shell');
%q(3) = patch([1500 2400 2400 1500]/1e3,[1e-6 1e-6 1 1],'g','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Kr L-shell');
set(gca,'TickDir','out');
grid on;
xlim([0.1 10]);
xlabel('Photon Energy (keV)');
%ylim([1e-4 1.0]);
% set(gca, 'YScale', 'log');
ylim([0 1.0]);
ylabel('Transmission');
[~, lgd] = legend([p q(1)],'Location','southeast','FontSize',14);
%[~, lgd] = legend([p],'Location','southeast','FontSize',14);
% legend_patches = findobj(lgd, 'type', 'patch');
% set(legend_patches(1), 'FaceAlpha', 0.3);
% set(legend_patches(2), 'FaceAlpha', 0.3);
% set(legend_patches(3), 'FaceAlpha', 0.3);
lgdline = findobj(lgd, 'type', 'line');
 
% %% Figure 2 with Ross pairs
% fig2 = figure('Name','Ross pairs','Units','normalized','Position',[0.1 0.18 0.85 0.7]);
% set(groot,'CurrentFigure',fig2);
% set(gca,'FontSize',28);
% hold on;
% p(1) = plot(filters(1).Eint,filters(1).Tint-filters(2).Tint,'-','Color',lines_col(1,:),'LineWidth',1.5,'DisplayName',[filters(1).label '-' filters(2).label]);
% p(2) = plot(filters(2).Eint,filters(2).Tint-filters(1).Tint,'--','Color',lines_col(1,:),'LineWidth',1.5,'DisplayName',[filters(2).label '-' filters(1).label]);
% p(3) = plot(filters(4).Eint,filters(4).Tint-filters(3).Tint,'-','Color',lines_col(2,:),'LineWidth',1.5,'DisplayName',[filters(4).label '-' filters(3).label]);
% p(4) = plot(filters(3).Eint,filters(3).Tint-filters(4).Tint,'--','Color',lines_col(2,:),'LineWidth',1.5,'DisplayName',[filters(3).label '-' filters(4).label]);
% p(5) = plot(filters(4).Eint,filters(4).Tint-filters(5).Tint,'-','Color',lines_col(3,:),'LineWidth',1.5,'DisplayName',[filters(4).label '-' filters(5).label]);
% p(6) = plot(filters(5).Eint,filters(5).Tint-filters(4).Tint,'--','Color',lines_col(3,:),'LineWidth',1.5,'DisplayName',[filters(5).label '-' filters(4).label]);
% p(7) = plot(filters(5).Eint,filters(5).Tint-filters(6).Tint,'-','Color',lines_col(4,:),'LineWidth',1.5,'DisplayName',[filters(5).label '-' filters(6).label]);
% p(8) = plot(filters(6).Eint,filters(6).Tint-filters(5).Tint,'--','Color',lines_col(4,:),'LineWidth',1.5,'DisplayName',[filters(6).label '-' filters(5).label]);
% p(9) = plot(filters(2).Eint,filters(2).Tint-filters(7).Tint,'-','Color',lines_col(5,:),'LineWidth',1.5,'DisplayName',[filters(2).label '-' filters(7).label]);
% p(10) = plot(filters(7).Eint,filters(7).Tint-filters(2).Tint,'--','Color',lines_col(5,:),'LineWidth',1.5,'DisplayName',[filters(7).label '-' filters(2).label]);
% % plot([850 850],[1e-6 1],'--b');
% % plot([1400 1400],[1e-6 1],'--b');
% % plot([3000 3000],[1e-6 1],'--r');
% % plot([4000 4000],[1e-6 1],'--r');
% % plot([1500 1500],[1e-6 1],'--g');
% % plot([2400 2400],[1e-6 1],'--g');
% q(1) = patch([850 1400 1400 850],[1e-6 1e-6 1 1],'b','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Ne K-shell');
% q(2) = patch([3000 4000 4000 3000],[1e-6 1e-6 1 1],'r','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Ar K-shell');
% q(3) = patch([1500 2400 2400 1500],[1e-6 1e-6 1 1],'g','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Kr L-shell');
% plot([0 10000],[0.1 0.1],'-k');
% set(gca,'TickDir','out');
% box on;
% grid on;
% xlim([100 7100]);
% ylim([1.0e-4 1.0]);
% set(gca, 'YScale', 'log');
% xlabel('Photon Energy (eV)');
% ylabel('Transmission Coefficient');
% [~, lgd] = legend([p q],'Location','southeast','FontSize',14);
% legend_patches = findobj(lgd, 'type', 'patch');
% set(legend_patches(1), 'FaceAlpha', 0.3);
% set(legend_patches(2), 'FaceAlpha', 0.3);
% set(legend_patches(3), 'FaceAlpha', 0.3);
% legend_lines = findobj(lgd, 'type', 'line');
% %Echeck = 2000;
% %fprintf('Window peak transmission = %.2f\n',filters(1).Tint(filters(1).Eint==Echeck)-filters(2).Tint(filters(1).Eint==Echeck));
% fprintf('\n');close all;
clearvars;
%clc;
filter_list = {'Sc_30um','V_13um','Ru_8.5um'};
%filter_list = {'Be_10um','B_10um','C_5um','Mg_10um','Al_10um','Ti_12um','V_10um'};
%filter_list = {'Ti_12um','V_10um','Cr_3um','Fe_10um','Cu_10um','Zr_25um','Nb_20um'}
%filter_list = {'Zr_25um','Nb_20um','Mo_7um','Ag_5um','Sn_15um','Ta_3um','W_10um'}
%filter_list = {'Si_10um','Si_5um','Cr_3um','Fe_5um'}
mpath = mfilename('fullpath');
[path, sciptname] = fileparts(mpath);
addpath(genpath(path));
workdir = path;
cd (workdir);
filters = struct;
energy = 10:5:10000;
file_found = struct;
for n_f = 1:length(filter_list)
    strpos = strfind(filter_list{n_f},'_');
    mat_look = filter_list{n_f}(1:strpos-1);
    file_found = dir([filter_list{n_f} '.txt']);
    if isempty(file_found)
        mat_found = dir([mat_look '*']);
        n_d = 0;
        if ~isempty(mat_found)
            while n_d < length(mat_found)
                n_d = n_d +1;
                strpos = strfind(mat_found(n_d).name,'_');
                mat_found(n_d).mat = mat_found(n_d).name(1:strpos-1);
                if ~strcmp(mat_found(n_d).mat,mat_look)
                    mat_found(n_d) = [];
                    n_d = n_d -1;
                else
                    file_found = mat_found(n_d);
                end
            end
        end
    end
    %file_found.str = sscanf(file_found.name,'%s_%fum.txt');
    strpos = strfind(file_found.name,'_');
    file_found.thick = str2double(file_found.name(strpos+1:end-6));
    strpos = strfind(filter_list{n_f},'_');
    data = importdata(file_found.name);
    filters(n_f).filter_string = data.textdata{1,1};
    string_values = textscan(filters(n_f).filter_string,' %s Density=%f Thickness=%f microns');
    filters(n_f).material = char(string_values{1});
    filters(n_f).density = string_values{2};
    filters(n_f).thickness = string_values{3};
    filters(n_f).thickness_ask = str2double(filter_list{n_f}(strpos+1:end-2));
    filters(n_f).rescale = filters(n_f).thickness_ask/filters(n_f).thickness;
    filters(n_f).thickness_rescaled = filters(n_f).thickness*filters(n_f).rescale;
    filters(n_f).label = char(strcat(filters(n_f).material,{' '},num2str(filters(n_f).thickness_rescaled),{'um'}));
    filters(n_f).E = data.data(:,1);
    filters(n_f).T = data.data(:,2).^filters(n_f).rescale;
    filters(n_f).Eint = energy;
    filters(n_f).Tint = interp1(filters(n_f).E,filters(n_f).T,filters(n_f).Eint,'pchip');
end
lines_col = lines;
%% Figure 1 with filter transmission
%fig1 = figure('Name','Filter Transmission','Position',[50 50 1450 720]);
fig1 = figure('Name','Filter Transmission','Units','normalized','Position',[0.1 0.18 0.85 0.7]);
set(groot,'CurrentFigure',fig1);
set(gca,'FontSize',24);
hold on;
for n_f = 1:length(filter_list)
    p(n_f) = plot(filters(n_f).Eint/1e3,filters(n_f).Tint,'-','LineWidth',2,'DisplayName',filters(n_f).label); %#ok<SAGROW>
end
q(1) = patch([4100 4900 4900 4100]/1e3,[1e-6 1e-6 1 1],'b','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Xe L-shell');
%q(2) = patch([3000 3200 3200 3000]/1e3,[1e-6 1e-6 1 1],'r','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Ar K-shell');
%q(3) = patch([1500 2400 2400 1500]/1e3,[1e-6 1e-6 1 1],'g','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Kr L-shell');
set(gca,'TickDir','out');
grid on;
xlim([0.1 10]);
xlabel('Photon Energy (keV)');
%ylim([1e-4 1.0]);
% set(gca, 'YScale', 'log');
ylim([0 1.0]);
ylabel('Transmission');
[~, lgd] = legend([p q(1)],'Location','southeast','FontSize',14);
%[~, lgd] = legend([p],'Location','southeast','FontSize',14);
% legend_patches = findobj(lgd, 'type', 'patch');
% set(legend_patches(1), 'FaceAlpha', 0.3);
% set(legend_patches(2), 'FaceAlpha', 0.3);
% set(legend_patches(3), 'FaceAlpha', 0.3);
lgdline = findobj(lgd, 'type', 'line');
% %% Figure 2 with Ross pairs
% fig2 = figure('Name','Ross pairs','Units','normalized','Position',[0.1 0.18 0.85 0.7]);
% set(groot,'CurrentFigure',fig2);
% set(gca,'FontSize',28);
% hold on;
% p(1) = plot(filters(1).Eint,filters(1).Tint-filters(2).Tint,'-','Color',lines_col(1,:),'LineWidth',1.5,'DisplayName',[filters(1).label '-' filters(2).label]);
% p(2) = plot(filters(2).Eint,filters(2).Tint-filters(1).Tint,'--','Color',lines_col(1,:),'LineWidth',1.5,'DisplayName',[filters(2).label '-' filters(1).label]);
% p(3) = plot(filters(4).Eint,filters(4).Tint-filters(3).Tint,'-','Color',lines_col(2,:),'LineWidth',1.5,'DisplayName',[filters(4).label '-' filters(3).label]);
% p(4) = plot(filters(3).Eint,filters(3).Tint-filters(4).Tint,'--','Color',lines_col(2,:),'LineWidth',1.5,'DisplayName',[filters(3).label '-' filters(4).label]);
% p(5) = plot(filters(4).Eint,filters(4).Tint-filters(5).Tint,'-','Color',lines_col(3,:),'LineWidth',1.5,'DisplayName',[filters(4).label '-' filters(5).label]);
% p(6) = plot(filters(5).Eint,filters(5).Tint-filters(4).Tint,'--','Color',lines_col(3,:),'LineWidth',1.5,'DisplayName',[filters(5).label '-' filters(4).label]);
% p(7) = plot(filters(5).Eint,filters(5).Tint-filters(6).Tint,'-','Color',lines_col(4,:),'LineWidth',1.5,'DisplayName',[filters(5).label '-' filters(6).label]);
% p(8) = plot(filters(6).Eint,filters(6).Tint-filters(5).Tint,'--','Color',lines_col(4,:),'LineWidth',1.5,'DisplayName',[filters(6).label '-' filters(5).label]);
% p(9) = plot(filters(2).Eint,filters(2).Tint-filters(7).Tint,'-','Color',lines_col(5,:),'LineWidth',1.5,'DisplayName',[filters(2).label '-' filters(7).label]);
% p(10) = plot(filters(7).Eint,filters(7).Tint-filters(2).Tint,'--','Color',lines_col(5,:),'LineWidth',1.5,'DisplayName',[filters(7).label '-' filters(2).label]);
% % plot([850 850],[1e-6 1],'--b');
% % plot([1400 1400],[1e-6 1],'--b');
% % plot([3000 3000],[1e-6 1],'--r');
% % plot([4000 4000],[1e-6 1],'--r');
% % plot([1500 1500],[1e-6 1],'--g');
% % plot([2400 2400],[1e-6 1],'--g');
% q(1) = patch([850 1400 1400 850],[1e-6 1e-6 1 1],'b','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Ne K-shell');
% q(2) = patch([3000 4000 4000 3000],[1e-6 1e-6 1 1],'r','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Ar K-shell');
% q(3) = patch([1500 2400 2400 1500],[1e-6 1e-6 1 1],'g','FaceAlpha',0.2,'EdgeColor','none','DisplayName','Kr L-shell');
% plot([0 10000],[0.1 0.1],'-k');
% set(gca,'TickDir','out');
% box on;
% grid on;
% xlim([100 7100]);
% ylim([1.0e-4 1.0]);
% set(gca, 'YScale', 'log');
% xlabel('Photon Energy (eV)');
% ylabel('Transmission Coefficient');
% [~, lgd] = legend([p q],'Location','southeast','FontSize',14);
% legend_patches = findobj(lgd, 'type', 'patch');
% set(legend_patches(1), 'FaceAlpha', 0.3);
% set(legend_patches(2), 'FaceAlpha', 0.3);
% set(legend_patches(3), 'FaceAlpha', 0.3);
% legend_lines = findobj(lgd, 'type', 'line');
% %Echeck = 2000;
% %fprintf('Window peak transmission = %.2f\n',filters(1).Tint(filters(1).Eint==Echeck)-filters(2).Tint(filters(1).Eint==Echeck));
% fprintf('\n');

Answer 1

[Walter Roberson]

file_found = dir([filter_list{n_f} '.txt']);

That is returning empty

if isempty(file_found)

So that branch is executed

        file_found = mat_found(n_d);

But that does not happen to get executed -- perhaps mat_found = dir([mat_look '*']) is returning empty.

strpos = strfind(file_found.name,'_');

file_found is empty, so file_found.name is expanding to 0 arguments, so the call is effectively to strfind('_')

You also have the more general problem that find_found might happen to match multiple files, so file_found.name might expand to multiple parameters.