strread函数读数据，出现索引超出 矩阵维度。

fid = fopen('w.txt', 'r');
fid_n=fopen('ex.dat','w');
while ~feof(fid)
    tline=fgetl(fid);
    if ~isempty(tline)
        if double(tline(1))>=48 && double(tline(1))<=57  %数值开始
            a=strread(tline);
            a(3:4)=[];
            fprintf(fid_n,'%f %f\n',a);
            clear a;
        elseif double(tline(1))==67   %字母C开始
           [b1,b2,b3,b4]=strread(tline,'%s %s %s %s');
           b=[b1{1},' ',b2{1}];
            fprintf(fid_n,'%s\n',b);
            clear b b1 b2 b3 b4;
        else
            fprintf(fid_n,'%s\n',tline);
        end
    else
        fprintf(fid_n,'%s\n',tline);
    end
end
fclose(fid);
fclose(fid_n);![这个是要读取的w.txt的文本](https://img-ask.csdn.net/upload/201907/26/1564151751_529109.png)![问题出在第14行但是不知如何改。](https://img-ask.csdn.net/upload/201907/26/1564151783_353861.png)