如何在tensorflow和/或numpy中有效地有效地实现以下功能？
add_along_axis(tensor=T, vector=v, axis=k)
# T is a tensor of shape (N1,...,Nd) (unknown beforehand)
# v is a vector with N components
# k is an integer such that Nk=N
S = T+v, summed along k
return S
即S是具有组件(N1,..,Nd)的{{1}}张量
请注意，S[i1,...,id]=T[i1,...,id] + v[ik]，Nj的任意数目都可能恰好等于j≠k，因此标准广播不是一种选择。
示例：让N和T = np.zeros( (3,3,3) )然后正确的输出应该是
v = [1,2,3]在这里，可以通过分别编写f(T,v,1) = [[[1., 1., 1.], [[2., 2., 2.], [[3., 3., 3.],
[1., 1., 1.], [2., 2., 2.], [3., 3., 3.],
[1., 1., 1.]], [2., 2., 2.]], [3., 3., 3.]]]
f(T,v,2) = [[[1., 1., 1.], [[1., 1., 1.], [[1., 1., 1.],
[2., 2., 2.], [2., 2., 2.], [2., 2., 2.],
[3., 3., 3.]], [3., 3., 3.]], [3., 3., 3.]]]
f(T,v,3) = [[[1., 2., 3.], [[1., 2., 3.], [[1., 2., 3.],
[1., 2., 3.], [1., 2., 3.], [1., 2., 3.],
[1., 2., 3.]], [1., 2., 3.]], [1., 2., 3.]]]
，T+v[:,None,None]和T+v[None,:,None]来实现目标行为。但是，在未预定义张量形状的情况下，我看不到这种方法如何工作。
答案 0 :(得分：0)
通过执行以下列表理解，您可以为T的任意尺寸和任何轴import {Component, ElementRef, OnInit, ViewChild} from '@angular/core';
import {ActivatedRoute, Params} from "@angular/router";
import {FormControl, FormGroup, Validators} from "@angular/forms";
import {CategoriesService} from "../../shared/services/categories.service";
import {switchMap} from "rxjs/operators";
import {of} from "rxjs";
import {MaterialService} from "../../shared/classes/material.service";
import {Category} from "../../shared/interfaces";
@Component({
selector: 'app-categories-form',
templateUrl: './categories-form.component.html',
styleUrls: ['./categories-form.component.css']
})
export class CategoriesFormComponent implements OnInit {
@ViewChild('input') inputRef: ElementRef
form: FormGroup
image: File
imagePreview=''
isNew= true
category: Category
constructor(private route: ActivatedRoute,
private categoriesService: CategoriesService) { }
ngOnInit() {
this.form=new FormGroup({
name:new FormControl(null, Validators.required)
})
this.form.disable()
this.route.params
.pipe(
switchMap(
(params: Params)=>{
if(params['id']){
this.isNew=false
return this.categoriesService.getById(params['id'])
}
return of (null)
}
)
)
.subscribe(
(category: Category)=>{
if(category){
this.category = category
this.form.patchValue({
name: category.name
})
this.imagePreview=category.imageSrc
MaterialService.updateTextInputs()
}
this.form.enable()
},
error=>MaterialService.toast(error.error.message)
)
}
triggerClick(){
this.inputRef.nativeElement.click()
}
onFileUpload(event: any){
const file = event.target.files[0]
this.image = file
const reader = new FileReader()
reader.onload = () => {
this.imagePreview = reader.result as string
}
reader.readAsDataURL(file)
}
onSubmit(){
let obs$
this.form.disable()
if(this.isNew){
obs$ = this.categoriesService.create(this.form.value.name, this.image)
} else {
obs$ = this.categoriesService.update(this.category._id, this.form.value.name, this.image)
}
obs$.subscribe(
category =>{
this.category = category
MaterialService.toast('Изменения сохранены!')
this.form.enable()
},
error=>{
MaterialService.toast(error.error.message)
this.form.enable()
}
)
}
}
自动生成create(name: string, image?:File) : Observable<Category>{
const fd = new FormData()
if(image){
fd.append('image', image.name)
}
fd.append('name', name)
return this.http.post<Category>('/api/category', fd)
}
update(id: string, name: string, image?:File) : Observable<Category>{
const fd= new FormData()
if(image){
fd.append('image', image.name)
}
fd.append('name', name)
return this.http.patch<Category>(`/api/category/${id}`, fd)
}
，
v[:,None,None] k等效于def f(T,v,k):
return T+v[[np.newaxis if i+1 != k else slice(None) for i in range(T.ndim) ]]
，而np.newaxis等效于None。结果与预期的一样：
slice(None)答案 1 :(得分：0)
只需将T.ndim-k的单位长度尺寸附加到v和numpy的广播规则上即可：
def f(T, v, k):
v = asarray(v)
return T + v.reshape(v.shape + (1,)*(T.ndim-k))
请注意，您对k的定义比标准的numpy轴编号大一；您可以考虑将k减1并将其称为“轴”。