Question

这是我的MATLAB代码：

mu_n = Tnume_mu/Tdeno_mu;

当我运行它时，它始终显示0，尽管变量Tnume_mu = 255和Tdeno_mu = 1.7957e4。

Answer 1

你检查了变量的类吗？

>> x = int32(5);
>> y = int32(10);
>> class(x)
int32
>> class(y)
int32
>> x / y
0

但

>> x = 5;
>> y = 10;
>> class(x)
double
>> class(y)
double
>> x / y
0.5

整数变量（int8，int16，int32，int64）只能取整数值，并且在除法期间舍入为零，因此如果结果将介于0和1之间，然后结果为0。

Answer 2

为了简化问题，我将使用更简单的变量名称和数字：

A = magic(2); B = magic(2).'; C = A./B; C = 1.0000 0.7500 1.3333 1.0000运算符是Using annotations的捷径。这是两个标量之间的常规划分。您可以将其扩展为矩阵，例如

./

\确保您明确划分元素。

还有另一个部门，即左 -divide：rdivide，或简称C = A^-1 * B。这是一个特定的MATLAB运算符，矩阵乘法通常用A^-1表示，其中A是矩阵C=A\B C = 0.7000 -0.2000 0.1000 1.4000 D = inv(A)*B; C == D 1的反函数。这个算子的优点在于它不会明确计算逆，而是对它进行******分解，使其更快，更强大。这不是问题，因为您很少需要矩阵的显式逆，您可以通过ldivide创建矩阵：

static class FirmwareDownload extends AsyncTask<String, String, String> {

        public String TAG = "Super LOG";
        public String file;
        int lenghtOfFile;
        long total;

        @Override
        protected String doInBackground(String... f_url) {
            try {
                int count;
                Utilies.getInternet();

                URL url = new URL(f_url[0]);
                URLConnection connection = url.openConnection();
                connection.connect();
                lenghtOfFile = connection.getContentLength();
                mProgressBar.setMax(lenghtOfFile);
                InputStream input = new BufferedInputStream(url.openStream(), 8192);
                String fileName = f_url[0].substring(f_url[0].lastIndexOf("/"), f_url[0].length());
                File root = Environment.getExternalStorageDirectory();
                File dir = new File(root.getAbsolutePath() + fileName);

                Log.d(TAG, "trying to download in : " + dir);
                dir.getAbsolutePath();
                OutputStream output = new FileOutputStream(dir);
                byte data[] = new byte[1024];


                while ((count = input.read(data)) != -1) {

                    if (isCancelled())
                        break;

                    total += count;
                    mProgressBar.setProgress(Integer.parseInt("" + total));
                    Log.d("Downloading " + fileName + " : ", " " + (int) ((total * 100) / lenghtOfFile));
                    mPercentage.post(new Runnable() {
                        @Override
                        public void run() {
                            mPercentage.setText(total / (1024 * 1024) + " Mb / " + lenghtOfFile / (1024 * 1024) + " Mb");
                        }
                    });
                    output.write(data, 0, count);
                }

                output.flush();
                output.close();
                input.close();

                //new InstallHelper().commandLine("mkdir data/data/ota");

                File fDest = new File("/data/data/ota/" + fileName);
                copyFile(dir, fDest);
                FirmwareInstaller fw = new FirmwareInstaller();
                fw.updateFirmware();

            } catch (Exception a) {
                System.out.println("Error trying donwloading firmware " + a);
                new InstallHelper().commandLine("rm -r  data/data/ota");
                dialog.dismiss();

            }
            return null;
        }

    }

为什么两个有限数的除法归零？

2 个答案: