title: RuntimeError: Given groups=1, weight of size [64, 3, 7, 7], expected input[3, 1, 224, 224] to have 3 channels, but got 1 channels instead
body: <p>In the code below:</p>
  
  <pre><code>    model_ft.eval()
      test_data, test_target = image_datasets['train'][idx]
      test_data = test_data.cuda()
      #test_target = test_target.cuda()
      test_target = torch.tensor(test_target)
      test_target = test_target.cuda()
      test_data.unsqueeze_(1)
      test_target.unsqueeze_(0)
      print(test_data.shape)
      output = model_ft(test_data)
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "test_loocv.py", line 245, in &lt;module&gt;
      output = model_ft(test_data)
    File "/scratch/sjn-p3/anaconda/anaconda3/lib/python3.6/site-packages/torch/nn/modules/module.py", line 477, in __call__
      result = self.forward(*input, **kwargs)
    File "/scratch/sjn-p3/anaconda/anaconda3/lib/python3.6/site-packages/torchvision-0.2.1-py3.6.egg/torchvision/models/resnet.py", line 139, in forward
    File "/scratch/sjn-p3/anaconda/anaconda3/lib/python3.6/site-packages/torch/nn/modules/module.py", line 477, in __call__
      result = self.forward(*input, **kwargs)
    File "/scratch/sjn-p3/anaconda/anaconda3/lib/python3.6/site-packages/torch/nn/modules/conv.py", line 301, in forward
      self.padding, self.dilation, self.groups)
  RuntimeError: Given groups=1, weight of size [64, 3, 7, 7], expected input[3, 1, 224, 224] to have 3 channels, but got 1 channels instead
  </code></pre>
  
  <p>Also, test_data has the shape: torch.Size([3, 1, 224, 224]).</p>
  
  <p>How should I fix this?</p>