Question

我正在学习如何使用numpy矩阵函数，我遇到了问题。

我有一个n个整数的列表，以及一个n行的矩阵。我需要将列表中的每个数字添加到矩阵中相应行的开头。

所以，如果我有以下矩阵和列表：

newMatrix = [[10, 0, 13],
             [11, 13, 0]]

我想要的输出是：

for c in range(len(myList)):
    newMatrix = np.insert(m[c],[0],myList[c])

这是我到目前为止的代码（尝试复制this page上的最后一个示例）：

    package com.apps.androidapps10;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;

import android.os.Environment;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.EditText;
import android.view.View;
import android.widget.Spinner;
import android.widget.Toast;


public class Main2Activity extends AppCompatActivity {

    Button hantarBtn;
    private static final String TAG = "MEDIA";
    String namaJalan = "";
    String namaLorong = "";
    String noKenderaan;
    private String filename = "SampleFile.txt";
    private String filepath = "MyFileStroage";
    File myExternalFile;
    EditText inputText;
    String separator = System.getProperty("line.separator");
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Intent intent = getIntent();
        setContentView(R.layout.activity_main2);

        hantarBtn = (Button) findViewById(R.id.button);
        inputText = (EditText) findViewById(R.id.editText);

        try {

            BufferedReader bReader =  new BufferedReader(new InputStreamReader
                    (getAssets().open("jalan.txt")));
            ArrayList<String> jalan = new ArrayList<String>();
            String line = bReader.readLine();
            while (line != null){
                jalan.add(line);
                line = bReader.readLine();

            }

            bReader.close();

            Spinner spinner1 = (Spinner) findViewById(R.id.spinner);
            ArrayAdapter<String> adapter1 =  new ArrayAdapter<String>(this,
                    android.R.layout.simple_spinner_dropdown_item,jalan);
            spinner1.setAdapter(adapter1);

            namaJalan = spinner1.getSelectedItem().toString();




        }catch (IOException e){

            e.printStackTrace();
        }

        try {
            BufferedReader bReader1 =  new BufferedReader(new InputStreamReader
                    (getAssets().open("lorong.txt")));
            ArrayList<String> lorong = new ArrayList<String>();
            String line = bReader1.readLine();
            while (line != null){
                lorong.add(line);
                line = bReader1.readLine();

            }

            bReader1.close();

            Spinner spinner2 = (Spinner) findViewById(R.id.spinner2);
            ArrayAdapter<String> adapter2 =  new ArrayAdapter<String>(this,
                    android.R.layout.simple_list_item_1,lorong);
            spinner2.setAdapter(adapter2);

            namaLorong = spinner2.getSelectedItem().toString();

        }catch (IOException e) {
            e.printStackTrace();
        }






        hantarBtn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                try {

                    FileOutputStream fos = new FileOutputStream(myExternalFile,true);
                    fos.write(inputText.getText().toString().getBytes());
                    fos.write("\t".getBytes());
                    fos.write(namaJalan.toString().getBytes());
                    fos.write("\t".getBytes());
                    fos.write(namaLorong.toString().getBytes());
                    fos.write("\r\n".getBytes());
                    fos.flush();
                    fos.close();


                    Toast.makeText(getApplicationContext(), "Write Done...",
                            Toast.LENGTH_SHORT).show();
                    //Intent intent = new Intent(Main2Activity.this, Main2Activity.class);
                    //startActivity(intent);
                } catch (Exception e) {
                    e.printStackTrace();
                    Log.i(TAG, "Failed to write");
                }

            }
        });

        if (!isExternalStorageAvailable() || isExternalStorageReadOnly()) {
            hantarBtn.setEnabled(false);
        } else {
            myExternalFile = new File(getExternalFilesDir(filepath), filename);
        }
    }

    private static boolean isExternalStorageReadOnly() {
        String extStorageState = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)) {
            return true;
        }
        return false;
    }

    private static boolean isExternalStorageAvailable() {
        String extStorageState = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(extStorageState)) {
            return true;
        }
        return false;
    }



}

但这当然只给出了for循环的最后一次迭代（[11,13,0]）。我想以某种方式将每一行附加到一个新的矩阵，但我似乎无法弄明白。

编辑：列表和矩阵的长度并不总是已知。

如果对numpy matrices更有经验的人知道更好的方法，我真的很感激！提前谢谢。

Answer 1

我的解决方案是：

import numpy as np

m = np.matrix([[0, 13], [13, 0]])
myList = [10, 11]
newmatrix = np.insert(m, 0, myList, axis=1)

输出是：

[[10  0 13]
 [11 13  0]]

Answer 2

一种选择是重塑myList，然后使用np.concatenate()功能：

import numpy as np

np.concatenate((np.array(myList).reshape(len(myList),1), m), axis = 1)
# matrix([[10,  0, 13],
#         [11, 13,  0]])

你也可以这样做：

np.concatenate((np.array(myList)[:, None], m), axis = 1)

# matrix([[10,  0, 13],
#         [11, 13,  0]])

将每个列表元素添加到numpy矩阵中每行的开头

2 个答案: